Update CMakeLists.txt

[Kreijstal]

fix #88 Simply adds conditions for when it is being compiled from mingw, and get the appropiate libraries

Summary of changes

1. Added MinGW Condition: Introduced a condition to check if the build environment is MinGW using ${CMAKE_CXX_PLATFORM_ID}.

   if ("${CMAKE_CXX_PLATFORM_ID}" STREQUAL "MinGW")
       ...
   endif()

2. Specified Library Paths for MinGW: Within the new MinGW condition, set the paths for the DirectX libraries (libdinput8.a, libxinput.a, libdxguid.a) directly using the $ENV{MSYSTEM_PREFIX} environment variable.

   set(DINPUT8_LIBRARY "$ENV{MSYSTEM_PREFIX}/lib/libdinput8.a")
   set(XINPUT8_LIBRARY "$ENV{MSYSTEM_PREFIX}/lib/libxinput.a")
   set(DXGUID_LIBRARY  "$ENV{MSYSTEM_PREFIX}/lib/libdxguid.a")

3. Added Checks for Library Existence: For added robustness, checks were inserted to ensure that the specified libraries actually exist on the file system.

   if (NOT EXISTS ${DINPUT8_LIBRARY})
       MESSAGE(FATAL_ERROR "Could not locate dinput8 DirectX library")
   endif()
   ...

4. Explicitly Linked Libraries for MinGW: Modified the target_link_libraries section to include a condition for MinGW, linking the libraries directly.

   target_link_libraries(OIS "$ENV{MSYSTEM_PREFIX}/lib/libdinput8.a" "$ENV{MSYSTEM_PREFIX}/lib/libxinput.a" "$ENV{MSYSTEM_PREFIX}/lib/libdxguid.a")

These changes aim to correctly configure and build the project when using MinGW, overriding any other settings that might point to incorrect paths for the DirectX libraries.

[Kreijstal]

the command changes to cmake -G "MSYS Makefiles" -H. -B./build

[Ybalrid]

looks good to me