Feature: Add guide to install system dependencies with pixi

Describe the enhancement or feature you would like

I've stopped using brew on my macOS and I'm instead using pixi whenever I need system-level dependencies. This works very well in practice even for building CPython and I can do things like pixi run configure and it automatically sets up all of the system dependencies and runs configure. Doing that requires setting some environment variables here and there, but I've done that in a pixi.toml and it's all automated. It looks somewhat like this:

[project]
name = "cpython-dev"
channels = ["conda-forge"]
platforms = ["osx-arm64"]

[dependencies]
gdbm = "*"
libmpdec-devel = "*"
openssl = "3.*"
pkg-config = "*"
tk = "*"
xz = "*"
zstd = "*"
zlib = "*"

[tasks.configure]
cmd = "./configure --with-openssl=$CONDA_PREFIX"

[tasks.configure.env]
PKG_CONFIG_PATH = "$CONDA_PREFIX/lib/pkgconfig"
GDBM_CFLAGS = "-I$CONDA_PREFIX/include"
GDBM_LIBS = "-L$CONDA_PREFIX/lib -lgdbm"
TCLTK_CFLAGS = "$(pkg-config --cflags tcl tk)"
# tcl.pc and tk.pc files contain stub libraries, but those do not extist
# in the conda package
TCLTK_LIBS = "$(pkg-config --libs tcl tk | sed 's/-l[^ ]*stub[^ ]*//g')"
LDFLAGS = "-Wl,-rpath,$CONDA_PREFIX/lib"

It's a bit too much to propose adding this to the CPython repo, at least for now. However, pointing to this as a way to install system-level dependencies in the devguide doesn't sounds like a bad idea to me.

Thoughts? Is there an appetite for this? If so, I can start drafting a PR.

Describe alternatives you have considered

No response

Additional context

No response

Start with the devguide's existing guidance for installing system-level dependencies and compare it with the proposed pixi.toml workflow. Add a concise pixi-based option or link covering the dependencies and environment setup shown in the issue, then verify that the development setup instructions are complete and understandable.