Building with Clang under a MinGW environment fails

[vittorioromeo]

Subject of the issue

Building using -DCMAKE_CXX_COMPILER=clang++ in a MinGW environment (e.g. installed via MSYS2) results in a compilation failure, because SFML's CMake files assume that when SFML_COMPILER_CLANG is TRUE then clang-cl is being used.

Your environment

• Windows 10, using a MinGW x64 environment obtained via MSYS2
• master branch of SFML
• clang version 11
• no special compiler flags

Steps to reproduce

1. Obtain MSYS2

2. Open a MSYS shell and install mingw-w64-x86_64-clang via pacman

3. Open a MinGW 64-bit shell and

   git clone https://github.com/SFML/SFML
   cd SFML
   mkdir build
   cd build
   cmake .. -G"MinGW Makefiles" -DCMAKE_CXX_COMPILER=clang++

4. Observe the compilation failure -- SFML tries to get libraries from libs-msvc-universal

[eXpl0it3r]

Looks like this is because of this rule

SFML/src/SFML/CMakeLists.txt

Lines 16 to 29 in 59df9d0

	elseif(SFML_COMPILER_MSVC OR SFML_COMPILER_CLANG)
	if(SFML_MSVC_VERSION LESS 14)
	if(ARCH_32BITS)
	set(CMAKE_LIBRARY_PATH ${CMAKE_LIBRARY_PATH} "${PROJECT_SOURCE_DIR}/extlibs/libs-msvc/x86")
	elseif(ARCH_64BITS)
	set(CMAKE_LIBRARY_PATH ${CMAKE_LIBRARY_PATH} "${PROJECT_SOURCE_DIR}/extlibs/libs-msvc/x64")
	endif()
	else()
	if(ARCH_32BITS)
	set(CMAKE_LIBRARY_PATH ${CMAKE_LIBRARY_PATH} "${PROJECT_SOURCE_DIR}/extlibs/libs-msvc-universal/x86")
	elseif(ARCH_64BITS)
	set(CMAKE_LIBRARY_PATH ${CMAKE_LIBRARY_PATH} "${PROJECT_SOURCE_DIR}/extlibs/libs-msvc-universal/x64")
	endif()
	endif()

If you can figure out a way to support clang-cl and clang msys/mingw I'd appreciate a PR!