cmake: fix minor 64BIT checks

CMakeLists.txt

@@ -59,7 +59,7 @@ if(CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT 64BIT)
 		error("UNDONE: set 32 build flags")
 	else()
 		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -m32")
-		set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CMAKE_C_FLAGS}")
+		set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32")
 		set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -m32")
 	endif()
 	set(CMAKE_SIZEOF_VOID_P 4)
@@ -73,7 +73,7 @@ endif()
 # see documentation: https://github.com/FWGS/xash3d-fwgs/blob/master/Documentation/library-naming.md
 include(LibraryNaming)
 
-if(64BIT)
+if(CMAKE_SIZEOF_VOID_P EQUAL 8)
 	message(STATUS "Building for 64 Bit")
 else()
 	message(STATUS "Building for 32 Bit")