Enable mingw CI job when compilation succeed

[charles-lunarg]

Currently, the mingw CI job fails with:

-- The C compiler identification is unknown
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - failed
-- Check for working C compiler: C:/msys64/mingw64/bin/cc.exe
CMake Error at C:/Program Files/CMake/share/cmake-3.31/Modules/CMakeTestCCompiler.cmake:67 (message):
  The C compiler
    "C:/msys64/mingw64/bin/cc.exe"
  is not able to compile a simple test program.

while attempting to generate the project solution. I investigated the issue but was unable to find a workable solution. In order to not prevent other PR's from making progress (or rather, not confuse actual CI failures with this one), I went ahead and disabled the mingw CI job for the time being.