Building issue Win10x64 Python3.7.1 / x64 / VS2017 / QL1.15 / Boost 1.69

Hi,

Win10x64
Python 3.7.1
VS 2017
QL 1.15
Boost 1.69 (prebuilt boost_1_69_0-msvc-14.1-64.exe)

I followed the following instructions
https://pyql.readthedocs.io/en/latest/getting_started.html#installation-from-source-on-windows

1/ Step f.
I get lots of warnings although VS says the .dll has been built with success.
Why so many warnings ? Can we fix this ?
```
...
1>c:\lib\quantlib-1.15\ql\settings.hpp(38): warning C4275: non dll-interface class 'boost::noncopyable_::noncopyable' used as base for dll-interface class 'QuantLib::Singleton' (compiling source file ql\settings.cpp)
1>c:\lib\boost_1_69_0\boost\core\noncopyable.hpp(38): note: see declaration of 'boost::noncopyable_::noncopyable' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(38): note: see declaration of 'QuantLib::Singleton' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(112): warning C4251: 'QuantLib::Settings::evaluationDate_': class 'QuantLib::Settings::DateProxy' needs to have dll-interface to be used by clients of class 'QuantLib::Settings' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(42): note: see declaration of 'QuantLib::Settings::DateProxy' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(114): warning C4251: 'QuantLib::Settings::includeTodaysCashFlows_': class 'boost::optional' needs to have dll-interface to be used by clients of class 'QuantLib::Settings' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(106): note: see declaration of 'boost::optional' (compiling source file ql\settings.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(38): warning C4275: non dll-interface class 'boost::noncopyable_::noncopyable' used as base for dll-interface class 'QuantLib::Singleton' (compiling source file ql\termstructure.cpp)
1>c:\lib\boost_1_69_0\boost\core\noncopyable.hpp(38): note: see declaration of 'boost::noncopyable_::noncopyable' (compiling source file ql\termstructure.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(38): note: see declaration of 'QuantLib::Singleton' (compiling source file ql\termstructure.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(112): warning C4251: 'QuantLib::Settings::evaluationDate_': class 'QuantLib::Settings::DateProxy' needs to have dll-interface to be used by clients of class 'QuantLib::Settings' (compiling source file ql\termstructure.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(42): note: see declaration of 'QuantLib::Settings::DateProxy' (compiling source file ql\termstructure.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(114): warning C4251: 'QuantLib::Settings::includeTodaysCashFlows_': class 'boost::optional' needs to have dll-interface to be used by clients of class 'QuantLib::Settings' (compiling source file ql\termstructure.cpp)
1>c:\lib\quantlib-1.15\ql\settings.hpp(106): note: see declaration of 'boost::optional' (compiling source file ql\termstructure.cpp)
1>Make build directory
1> Creating library .\lib\QuantLib-vc141-x64-mt.lib and object .\lib\QuantLib-vc141-x64-mt.exp
1>QuantLib.vcxproj -> C:\lib\QuantLib-1.15\.\lib\QuantLib-vc141-x64-mt.dll
1>Done building project "QuantLib.vcxproj".
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========
```
2/ Step g.
I struggle generating the .def file
As I get MSVC14.1 I had to do the following amendment %d1 instead of %d0 to get the correct folder
`input_directory = r"C:\lib\QuantLib-1.15\build\vc%d1\%s\Release" % ((VC_VERSION, ARCH))`
C:\lib\QuantLib-1.15\build\vc141\x64\Release

However, at this stage I get the following errors

```
runfile('C:/lib/pyql-master/scripts/generate_symbols.py', wdir='C:/lib/pyql-master/scripts')
QL_LIB: QuantLib-vc141-x64-mt
VC: 14.1
dir: C:\lib\QuantLib-1.15\build\vc141\x64\Release
Traceback (most recent call last):

File "", line 1, in
runfile('C:/lib/pyql-master/scripts/generate_symbols.py', wdir='C:/lib/pyql-master/scripts')
File "C:\ProgramData\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 704, in runfile
execfile(filename, namespace)
File "C:\ProgramData\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 108, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)
File "C:/lib/pyql-master/scripts/generate_symbols.py", line 101, in
main()
File "C:/lib/pyql-master/scripts/generate_symbols.py", line 97, in main
generate_deffile_from_dir(input_directory, output_file)
File "C:/lib/pyql-master/scripts/generate_symbols.py", line 87, in generate_deffile_from_dir
for symbol in process_directory(input_directory):
File "C:/lib/pyql-master/scripts/generate_symbols.py", line 63, in process_directory
for symbol in symbol_generator_from_obj_file(object_file):
File "C:/lib/pyql-master/scripts/generate_symbols.py", line 20, in symbol_generator_from_obj_file
nm_result = subprocess.check_output(command, startupinfo=startupinfo)
File "C:\ProgramData\Anaconda3\lib\subprocess.py", line 389, in check_output
**kwargs).stdout
File "C:\ProgramData\Anaconda3\lib\subprocess.py", line 466, in run
with Popen(*popenargs, **kwargs) as process:
File "C:\ProgramData\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 171, in __init__
super(SubprocessPopen, self).__init__(*args, **kwargs)
File "C:\ProgramData\Anaconda3\lib\subprocess.py", line 769, in __init__
restore_signals, start_new_session)
File "C:\ProgramData\Anaconda3\lib\subprocess.py", line 1172, in _execute_child
startupinfo)
FileNotFoundError: [WinError 2] The system cannot find the file specified

```

Any idea ?