Check if -mno-ms-bitfields is avail before using

CMakeLists.txt

@@ -8,6 +8,7 @@ endif()
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
 
 include(CMakeDependentOption)
+include(CheckCXXCompilerFlag)
 
 file(STRINGS src/version.h SRB2_VERSION)
 string(REGEX MATCH "[0-9]+\\.[0-9.]+" SRB2_VERSION ${SRB2_VERSION})

src/CMakeLists.txt

@@ -408,7 +408,10 @@ endif()
 # Compatibility flag with later versions of GCC
 # We should really fix our code to not need this
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-	target_compile_options(SRB2SDL2 PRIVATE -mno-ms-bitfields)
+	check_cxx_compiler_flag("-mno-ms-bitfields" HAS_MS_BITFIELDS)
+	if(HAS_MS_BITFIELDS)
+		target_compile_options(SRB2SDL2 PRIVATE -mno-ms-bitfields)
+	endif()
 endif()
 
 # Yes we know we use insecure CRT functions...