[CMAKE] Fix compiling i386 targets via x64 clang-cl

Author: SigmaTel71

toolchain-msvc.cmake

@@ -39,6 +39,9 @@ if(USE_CLANG_CL)
         set(CMAKE_C_COMPILER_TARGET "arm64-pc-windows-msvc")
         set(CMAKE_CXX_COMPILER_TARGET "arm64-pc-windows-msvc")
     else()
+        # -m32 is required for x64 clang-cl to operate in x86 Native Tools environment
+        set(CMAKE_C_FLAGS "-m32")
+        set(CMAKE_CXX_FLAGS "-m32")
         set(CMAKE_C_COMPILER_TARGET "i686-pc-windows-msvc")
         set(CMAKE_CXX_COMPILER_TARGET "i686-pc-windows-msvc")
     endif()