Adding flang as a fortran compiler

- [X] I read [the conda-forge documentation](https://conda-forge.org/docs/user/introduction.html#how-can-i-install-packages-from-conda-forge) and could not find the solution for my problem there.

Issue: `flang` is available as a compiler for fortran on Windows ([flang_win-64 feedstock](https://github.com/conda-forge/flang-feedstock)), but is not currently added as part of the options here in the `compilers` feedstock, so packages that require a fortran compiler on Windows get stuck on requesting vc14 and flang 5.0 for some reason:
```
Encountered problems while solving:
- nothing provides vc 14 needed by flang-5.0.0-vc14_1
```

Environment (conda list):

```
$ mamba list
# Name Version Build Channel
anyio 3.4.0 py39hcbf5309_0 conda-forge
argon2-cffi 21.1.0 py39hb82d6ee_2 conda-forge
arviz 0.11.4 pyhd8ed1ab_0 conda-forge
astroid 2.9.0 py39hcbf5309_0 conda-forge
async_generator 1.10 py_0 conda-forge
attrs 21.2.0 pyhd8ed1ab_0 conda-forge
autopep8 1.6.0 pyhd8ed1ab_1 conda-forge
babel 2.9.1 pyh44b312d_0 conda-forge
backcall 0.2.0 pyh9f0ad1d_0 conda-forge
backports 1.0 py_2 conda-forge
backports.functools_lru_cache 1.6.4 pyhd8ed1ab_0 conda-forge
bambi 0.6.3 pypi_0 pypi
blas 2.112 mkl conda-forge
blas-devel 3.9.0 12_win64_mkl conda-forge
bleach 4.1.0 pyhd8ed1ab_0 conda-forge
boost-cpp 1.77.0 h5b4e17d_1 conda-forge
brotli 1.0.9 h8ffe710_6 conda-forge
brotli-bin 1.0.9 h8ffe710_6 conda-forge
brotlipy 0.7.0 py39hb82d6ee_1003 conda-forge
bzip2 1.0.8 h8ffe710_4 conda-forge
ca-certificates 2021.10.8 h5b45459_0 conda-forge
cachetools 4.2.4 pyhd8ed1ab_0 conda-forge
cairo 1.16.0 hb19e0ff_1008 conda-forge
certifi 2021.10.8 py39hcbf5309_1 conda-forge
cffi 1.15.0 py39h0878f49_0 conda-forge
cftime 1.5.1.1 py39h5d4886f_1 conda-forge
chardet 4.0.0 py39hcbf5309_2 conda-forge
charset-normalizer 2.0.8 pyhd8ed1ab_0 conda-forge
clang 11.0.1 h57928b3_1 conda-forge
clang-11 11.0.1 default_h5c34c98_1 conda-forge
clang-tools 11.0.1 default_h5c34c98_1 conda-forge
clangdev 11.0.1 default_h5c34c98_1 conda-forge
clangxx 11.0.1 default_h5c34c98_1 conda-forge
colorama 0.4.4 pyh9f0ad1d_0 conda-forge
conda 4.11.0 py39hcbf5309_0 conda-forge
conda-package-handling 1.7.3 py39hb3671d1_1 conda-forge
cppad 20210000.8 h0e60522_0 conda-forge
cryptography 36.0.0 py39h7bc7c5c_0 conda-forge
curl 7.80.0 h789b8ee_0 conda-forge
cvxopt 1.2.7 py39h73f7814_1 conda-forge
cvxpy 1.1.17 py39hcbf5309_1 conda-forge
cvxpy-base 1.1.17 py39h2e25243_1 conda-forge
cycler 0.11.0 pyhd8ed1ab_0 conda-forge
debugpy 1.5.1 py39h415ef7b_0 conda-forge
decorator 5.1.0 pyhd8ed1ab_0 conda-forge
defusedxml 0.7.1 pyhd8ed1ab_0 conda-forge
dill 0.3.4 pyhd8ed1ab_0 conda-forge
dsdp 5.8 h6e01ec9_1203 conda-forge
ecos 2.0.8 py39h5d4886f_2 conda-forge
entrypoints 0.3 py39hde42818_1002 conda-forge
expat 2.4.1 h39d44d4_0 conda-forge
fastprogress 1.0.0 py_0 conda-forge
fftw 3.3.10 nompi_hb424310_101 conda-forge
filelock 3.4.0 pyhd8ed1ab_0 conda-forge
flake8 4.0.1 pyhd8ed1ab_0 conda-forge
flang 11.0.1 h0e60522_20210131 conda-forge
flang_win-64 11.0.1 h57928b3_20210131 conda-forge
font-ttf-dejavu-sans-mono 2.37 hab24e00_0 conda-forge
font-ttf-inconsolata 3.000 h77eed37_0 conda-forge
font-ttf-source-code-pro 2.038 h77eed37_0 conda-forge
font-ttf-ubuntu 0.83 hab24e00_0 conda-forge
fontconfig 2.13.1 h1989441_1005 conda-forge
fonts-conda-ecosystem 1 0 conda-forge
fonts-conda-forge 1 0 conda-forge
fonttools 4.28.2 py39hb82d6ee_0 conda-forge
formulae 0.2.0 pypi_0 pypi
freetype 2.10.4 h546665d_1 conda-forge
fribidi 1.0.10 h8d14728_0 conda-forge
getopt-win32 0.1 h8ffe710_0 conda-forge
gettext 0.19.8.1 ha2e2712_1008 conda-forge
glpk 4.65 h8ffe710_1004 conda-forge
graphite2 1.3.13 1000 conda-forge
graphviz 2.49.3 hefbd956_0 conda-forge
gsl 2.7 hdfb1a43_0 conda-forge
gts 0.7.6 h7c369d9_2 conda-forge
harfbuzz 3.1.1 hc601d6f_0 conda-forge
hdf4 4.2.15 h0e5069d_3 conda-forge
hdf5 1.12.1 nompi_h2a0e4a3_102 conda-forge
icu 68.2 h0e60522_0 conda-forge
idna 3.1 pyhd3deb0d_0 conda-forge
importlib-metadata 4.8.2 py39hcbf5309_0 conda-forge
importlib_metadata 4.8.2 hd8ed1ab_0 conda-forge
importlib_resources 5.4.0 pyhd8ed1ab_0 conda-forge
intel-openmp 2021.4.0 h57928b3_3556 conda-forge
ipopt 3.11.1 2 conda-forge
ipykernel 6.5.1 py39h832f523_0 conda-forge
ipython 7.30.0 py39hcbf5309_0 conda-forge
ipython_genutils 0.2.0 py_1 conda-forge
isort 5.10.1 pyhd8ed1ab_0 conda-forge
jbig 2.1 h8d14728_2003 conda-forge
jedi 0.18.1 py39hcbf5309_0 conda-forge
jinja2 3.0.3 pyhd8ed1ab_0 conda-forge
joblib 1.1.0 pyhd8ed1ab_0 conda-forge
jpeg 9d h8ffe710_0 conda-forge
json5 0.9.5 pyh9f0ad1d_0 conda-forge
jsonschema 4.2.1 pyhd8ed1ab_0 conda-forge
jupyter-lsp 1.5.0 pyhd8ed1ab_0 conda-forge
jupyter_client 7.1.0 pyhd8ed1ab_0 conda-forge
jupyter_core 4.9.1 py39hcbf5309_1 conda-forge
jupyter_server 1.12.1 pyhd8ed1ab_0 conda-forge
jupyterlab 3.2.4 pyhd8ed1ab_0 conda-forge
jupyterlab-drawio 0.9.0 pyhd8ed1ab_0 conda-forge
jupyterlab-lsp 3.9.1 pyhd8ed1ab_0 conda-forge
jupyterlab-mathjax3 4.2.2 pyhd8ed1ab_0 conda-forge
jupyterlab-spellchecker 0.7.2 pyhd8ed1ab_0 conda-forge
jupyterlab-variableinspector 3.0.9 pyhd8ed1ab_0 conda-forge
jupyterlab_pygments 0.1.2 pyh9f0ad1d_0 conda-forge
jupyterlab_server 2.8.2 pyhd8ed1ab_0 conda-forge
kiwisolver 1.3.2 py39h2e07f2f_1 conda-forge
krb5 1.19.2 h20d022d_3 conda-forge
lapack 3.9.0 netlib conda-forge
lazy-object-proxy 1.6.0 py39hb82d6ee_1 conda-forge
lcms2 2.12 h2a16943_0 conda-forge
lerc 3.0 h0e60522_0 conda-forge
libarchive 3.5.2 hb45042f_1 conda-forge
libblas 3.9.0 12_win64_mkl conda-forge
libbrotlicommon 1.0.9 h8ffe710_6 conda-forge
libbrotlidec 1.0.9 h8ffe710_6 conda-forge
libbrotlienc 1.0.9 h8ffe710_6 conda-forge
libcblas 3.9.0 12_win64_mkl conda-forge
libclang 11.0.1 default_h5c34c98_1 conda-forge
libclang-cpp 11.0.1 default_h5c34c98_1 conda-forge
libcurl 7.80.0 h789b8ee_0 conda-forge
libcxx 7.0.0 h1ad3211_1002 conda-forge
libdeflate 1.8 h8ffe710_0 conda-forge
libffi 3.4.2 h8ffe710_5 conda-forge
libflang 11.0.1 h0e60522_20210131 conda-forge
libgd 2.3.3 h8bb91b0_0 conda-forge
libglib 2.70.1 h3be07f2_0 conda-forge
libgpuarray 0.7.6 h8ffe710_1003 conda-forge
libiconv 1.16 he774522_0 conda-forge
liblapack 3.9.0 12_win64_mkl conda-forge
liblapacke 3.9.0 12_win64_mkl conda-forge
libllvm11 11.0.1 hab3b255_0 conda-forge
libmamba 0.19.0 h44daa3b_0 conda-forge
libmambapy 0.19.0 py39h9c8ecf5_0 conda-forge
libnetcdf 4.8.1 nompi_h1cc8e9d_101 conda-forge
libpng 1.6.37 h1d00b33_2 conda-forge
libpython 2.1 py39hcbf5309_1 conda-forge
libsodium 1.0.18 h8d14728_1 conda-forge
libsolv 0.7.19 h7755175_5 conda-forge
libssh2 1.10.0 h680486a_2 conda-forge
libtiff 4.3.0 hd413186_2 conda-forge
libwebp 1.2.1 h57928b3_0 conda-forge
libwebp-base 1.2.1 h8ffe710_0 conda-forge
libxcb 1.13 hcd874cb_1004 conda-forge
libxml2 2.9.12 hf5bbc77_1 conda-forge
libzip 1.8.0 hfed4ece_1 conda-forge
libzlib 1.2.11 h8ffe710_1013 conda-forge
llvm-meta 7.0.0 0 conda-forge
llvm-openmp 11.0.1 h2d74725_0 conda-forge
llvm-tools 11.0.1 hab3b255_0 conda-forge
llvmdev 11.0.1 hab3b255_0 conda-forge
llvmlite 0.37.0 py39ha0cd8c8_1 conda-forge
lz4-c 1.9.3 h8ffe710_1 conda-forge
lzo 2.10 he774522_1000 conda-forge
m2w64-gcc-libgfortran 5.3.0 6 conda-forge
m2w64-gcc-libs 5.3.0 7 conda-forge
m2w64-gcc-libs-core 5.3.0 7 conda-forge
m2w64-gmp 6.1.0 2 conda-forge
m2w64-libwinpthread-git 5.0.0.4634.697f757 2 conda-forge
mako 1.1.6 pyhd8ed1ab_0 conda-forge
mamba 0.19.0 py39hb3d9227_0 conda-forge
markupsafe 2.0.1 py39hb82d6ee_1 conda-forge
matplotlib 3.5.0 py39hcbf5309_0 conda-forge
matplotlib-base 3.5.0 py39h581301d_0 conda-forge
matplotlib-inline 0.1.3 pyhd8ed1ab_0 conda-forge
mccabe 0.6.1 py_1 conda-forge
menuinst 1.4.18 py39hcbf5309_1 conda-forge
miniforge_console_shortcut 2.0 h57928b3_1 conda-forge
mistune 0.8.4 py39hb82d6ee_1005 conda-forge
mkl 2021.4.0 h0e2418a_729 conda-forge
mkl-devel 2021.4.0 h57928b3_730 conda-forge
mkl-include 2021.4.0 h0e2418a_729 conda-forge
mkl-service 2.4.0 py39h6b0492b_0 conda-forge
msys2-conda-epoch 20160418 1 conda-forge
munkres 1.1.4 pyh9f0ad1d_0 conda-forge
nbclassic 0.3.4 pyhd8ed1ab_0 conda-forge
nbclient 0.5.9 pyhd8ed1ab_0 conda-forge
nbconvert 6.3.0 py39hcbf5309_1 conda-forge
nbformat 5.1.3 pyhd8ed1ab_0 conda-forge
nest-asyncio 1.5.1 pyhd8ed1ab_0 conda-forge
netcdf4 1.5.8 nompi_py39hf113b1f_101 conda-forge
notebook 6.4.6 pyha770c72_0 conda-forge
numba 0.54.1 py39hb8cd55e_0 conda-forge
numpy 1.20.3 py39h6635163_1 conda-forge
olefile 0.46 pyh9f0ad1d_1 conda-forge
openjpeg 2.4.0 hb211442_1 conda-forge
openssl 1.1.1l h8ffe710_0 conda-forge
osqp 0.6.2.post0 py39h2e25243_3 conda-forge
packaging 21.3 pyhd8ed1ab_0 conda-forge
pandas 1.3.4 py39h2e25243_1 conda-forge
pandoc 2.16.2 h8ffe710_0 conda-forge
pandocfilters 1.5.0 pyhd8ed1ab_0 conda-forge
pango 1.48.10 h33e4779_2 conda-forge
parso 0.8.3 pyhd8ed1ab_0 conda-forge
patsy 0.5.2 pyhd8ed1ab_0 conda-forge
pcre 8.45 h0e60522_0 conda-forge
pickleshare 0.7.5 py39hde42818_1002 conda-forge
pillow 8.4.0 py39h916092e_0 conda-forge
pip 21.3.1 pyhd8ed1ab_0 conda-forge
pixman 0.40.0 h8ffe710_0 conda-forge
platformdirs 2.3.0 pyhd8ed1ab_0 conda-forge
pluggy 1.0.0 py39hcbf5309_2 conda-forge
prometheus_client 0.12.0 pyhd8ed1ab_0 conda-forge
prompt-toolkit 3.0.22 pyha770c72_0 conda-forge
pthread-stubs 0.4 hcd874cb_1001 conda-forge
pybind11-abi 4 hd8ed1ab_3 conda-forge
pycodestyle 2.8.0 pyhd8ed1ab_0 conda-forge
pycosat 0.6.3 py39hb82d6ee_1009 conda-forge
pycparser 2.21 pyhd8ed1ab_0 conda-forge
pydocstyle 6.1.1 pyhd8ed1ab_0 conda-forge
pyflakes 2.4.0 pyhd8ed1ab_0 conda-forge
pygments 2.10.0 pyhd8ed1ab_0 conda-forge
pygpu 0.7.6 py39h5d4886f_1003 conda-forge
pylint 2.12.1 pyhd8ed1ab_0 conda-forge
pymc3 3.11.4 pypi_0 pypi
pyopenssl 21.0.0 pyhd8ed1ab_0 conda-forge
pyparsing 3.0.6 pyhd8ed1ab_0 conda-forge
pyqt 5.12.3 py39hcbf5309_8 conda-forge
pyqt-impl 5.12.3 py39h415ef7b_8 conda-forge
pyqt5-sip 4.19.18 py39h415ef7b_8 conda-forge
pyqtchart 5.12 py39h415ef7b_8 conda-forge
pyqtwebengine 5.12.1 py39h415ef7b_8 conda-forge
pyrsistent 0.18.0 py39hb82d6ee_0 conda-forge
pyscipopt 3.4.0 pypi_0 pypi
pysocks 1.7.1 py39hcbf5309_4 conda-forge
python 3.9.7 h7840368_3_cpython conda-forge
python-dateutil 2.8.2 pyhd8ed1ab_0 conda-forge
python-graphviz 0.19 pyhaef67bd_0 conda-forge
python-lsp-jsonrpc 1.0.0 pyhd8ed1ab_0 conda-forge
python-lsp-server 1.3.2 pyhd8ed1ab_0 conda-forge
python_abi 3.9 2_cp39 conda-forge
pytz 2021.3 pyhd8ed1ab_0 conda-forge
pywin32 302 py39hb82d6ee_2 conda-forge
pywinpty 1.1.6 py39h99910a6_0 conda-forge
pyzmq 22.3.0 py39he46f08e_1 conda-forge
qdldl-python 0.1.5 py39h2e25243_2 conda-forge
qt 5.12.9 h5909a2a_4 conda-forge
reproc 14.2.3 h8ffe710_0 conda-forge
reproc-cpp 14.2.3 h0e60522_0 conda-forge
requests 2.26.0 pyhd8ed1ab_1 conda-forge
requests-unixsocket 0.2.0 py_0 conda-forge
rope 0.22.0 pyhd8ed1ab_0 conda-forge
ruamel_yaml 0.15.80 py39hb82d6ee_1006 conda-forge
scikit-learn 1.0.1 py39he931e04_2 conda-forge
scipy 1.7.3 py39hc0c34ad_0 conda-forge
scs 3.0.0 py39hc73de48_1 conda-forge
seaborn 0.11.2 hd8ed1ab_0 conda-forge
seaborn-base 0.11.2 pyhd8ed1ab_0 conda-forge
semver 2.13.0 pyh9f0ad1d_0 conda-forge
send2trash 1.8.0 pyhd8ed1ab_0 conda-forge
setuptools 59.4.0 py39hcbf5309_0 conda-forge
simpy 4.0.1 pyhd8ed1ab_0 conda-forge
six 1.16.0 pyh6c4a22f_0 conda-forge
sniffio 1.2.0 py39hcbf5309_2 conda-forge
snowballstemmer 2.2.0 pyhd8ed1ab_0 conda-forge
sqlite 3.37.0 h8ffe710_0 conda-forge
statsmodels 0.13.1 py39h5d4886f_0 conda-forge
tbb 2021.4.0 h2d74725_1 conda-forge
tbb-devel 2021.4.0 h2d74725_1 conda-forge
terminado 0.12.1 py39hcbf5309_1 conda-forge
testpath 0.5.0 pyhd8ed1ab_0 conda-forge
theano-pymc 1.1.2 pypi_0 pypi
threadpoolctl 3.0.0 pyh8a188c0_0 conda-forge
tk 8.6.11 h8ffe710_1 conda-forge
toml 0.10.2 pyhd8ed1ab_0 conda-forge
tornado 6.1 py39hb82d6ee_2 conda-forge
tqdm 4.62.3 pyhd8ed1ab_0 conda-forge
traitlets 5.1.1 pyhd8ed1ab_0 conda-forge
typing-extensions 3.10.0.2 hd8ed1ab_0 conda-forge
typing_extensions 3.10.0.2 pyha770c72_0 conda-forge
tzdata 2021e he74cb21_0 conda-forge
ucrt 10.0.20348.0 h57928b3_0 conda-forge
ujson 4.2.0 py39h415ef7b_1 conda-forge
urllib3 1.26.7 pyhd8ed1ab_0 conda-forge
vc 14.2 hb210afc_5 conda-forge
vs2015_runtime 14.29.30037 h902a5da_5 conda-forge
wcwidth 0.2.5 pyh9f0ad1d_2 conda-forge
webencodings 0.5.1 py_1 conda-forge
websocket-client 1.2.1 py39hcbf5309_0 conda-forge
wheel 0.37.0 pyhd8ed1ab_1 conda-forge
win_inet_pton 1.1.0 py39hcbf5309_3 conda-forge
winpty 0.4.3 4 conda-forge
wrapt 1.13.3 py39hb82d6ee_1 conda-forge
xarray 0.20.1 pyhd8ed1ab_0 conda-forge
xorg-kbproto 1.0.7 hcd874cb_1002 conda-forge
xorg-libice 1.0.10 hcd874cb_0 conda-forge
xorg-libsm 1.2.3 hcd874cb_1000 conda-forge
xorg-libx11 1.7.2 hcd874cb_0 conda-forge
xorg-libxau 1.0.9 hcd874cb_0 conda-forge
xorg-libxdmcp 1.1.3 hcd874cb_0 conda-forge
xorg-libxext 1.3.4 hcd874cb_1 conda-forge
xorg-libxpm 3.5.13 hcd874cb_0 conda-forge
xorg-libxt 1.2.1 hcd874cb_2 conda-forge
xorg-xextproto 7.3.0 hcd874cb_1002 conda-forge
xorg-xproto 7.0.31 hcd874cb_1007 conda-forge
xz 5.2.5 h62dcd97_1 conda-forge
yaml 0.2.5 he774522_0 conda-forge
yaml-cpp 0.6.3 ha925a31_4 conda-forge
yapf 0.31.0 pyhd8ed1ab_0 conda-forge
zeromq 4.3.4 h0e60522_1 conda-forge
zipp 3.6.0 pyhd8ed1ab_0 conda-forge
zlib 1.2.11 h8ffe710_1013 conda-forge
zstd 1.5.0 h6255e5f_0 conda-forge
```

Details about conda and system ( conda info ):

```
$ conda info

(removed paths with my name)
active environment : base
shell level : 1
conda version : 4.11.0
conda-build version : not installed
python version : 3.9.7.final.0
virtual packages : __cuda=11.4=0
__win=0=0
__archspec=1=x86_64
platform : win-64
user-agent : conda/4.11.0 requests/2.26.0 CPython/3.9.7 Windows/10 Windows/10.0.19042
administrator : False
netrc file : None
offline mode : False
```

Compare the flang_win-64 feedstock linked in the issue with the compilers feedstock's existing compiler options and configuration. Reproduce the Windows solve that requests vc14 and flang 5.0, then verify that packages requiring a Fortran compiler resolve without the reported unavailable dependency.

Written by the indexing model from the issue text.