Re-enable mingw C++ test

[h-vetinari]

Descoped from #362, ran into

In file included from mytest.cxx:1:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\iostream:43:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\ostream:42:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\bits/ostream.h:43:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\ios:42:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\iosfwd:44:
In file included from %PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\bits/postypes.h:42:
%PREFIX%\Library\lib\gcc\x86_64-w64-mingw32\15.1.0\include\c++\cwchar:49:10: fatal error: 'wchar.h' file not found
   49 | #include <wchar.h>
      |          ^~~~~~~~~
1 error generated.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/16546516416. Examine the logs at this URL for more detail.}

[h-vetinari]

 "C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise\\VC\\Tools\\Llvm\\x64\\bin\\clang++.exe" -cc1 -triple x86_64-w64-windows-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name mytest.cxx -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -mms-bitfields -funwind-tables=2 -fno-sized-deallocation -fno-use-init-array -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb "-fdebug-compilation-dir=C:\\bld\\clang_packages_1752215595327\\test_tmp" -v "-fcoverage-compilation-dir=C:\\bld\\clang_packages_1752215595327\\test_tmp" -resource-dir "C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise\\VC\\Tools\\Llvm\\x64\\lib\\clang\\19" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++\\15.1.0" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++\\15.1.0\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include\\c++\\15.1.0\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\include\\c++\\15.1.0" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\include\\c++\\15.1.0\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\include\\c++\\15.1.0\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\c++" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\c++\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1.0" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1.0\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1.0\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15.1\\backward" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15\\x86_64-w64-mingw32" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\lib\\gcc\\x86_64-w64-mingw32\\15.1.0\\include\\g++-v15\\backward" -internal-isystem "C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise\\VC\\Tools\\Llvm\\x64\\lib\\clang\\19\\include" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\include" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\x86_64-w64-mingw32\\usr/include" -internal-isystem "C:\\bld\\clang_packages_1752215595327\\_test_env\\Library\\include" -fdeprecated-macro -ferror-limit 19 -fno-use-cxa-atexit -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -exception-model=seh -faddrsig -o "C:\\Users\\VSSADM~1\\AppData\\Local\\Temp\\mytest-960621.o" -x c++ mytest.cxx
clang -cc1 version 19.1.5 based upon LLVM 19.1.5 default target x86_64-pc-windows-msvc

I'm actually pretty sure this is due to conda-forge/conda-smithy#2319 and would be fixed by conda-forge/vc-feedstock#99

Nevermind, that's due to some random clang++ being on the PATH and getting picked up for the unactivated compilers.