It's better to use MSVC here instead of WIN32, so it wouldn't break MinGW builds

cl_dll/CMakeLists.txt

@@ -28,7 +28,7 @@ set (CLDLL_LIBRARY client)
 
 add_definitions(-DCLIENT_WEAPONS -DCLIENT_DLL)
 
-if(NOT WIN32)
+if(NOT MSVC)
 	add_compile_options(-fno-exceptions) # GCC/Clang flag
 	add_compile_options(-Wno-write-strings) # GCC/Clang flag
 	add_definitions(-D_LINUX -DLINUX) # It seems enough for all non-Win32 systems

dlls/CMakeLists.txt

@@ -27,7 +27,7 @@ set (SVDLL_LIBRARY server)
 
 add_definitions(-DCLIENT_WEAPONS)
 
-if(NOT WIN32)
+if(NOT MSVC)
 	add_compile_options(-fno-exceptions) # GCC/Clang flag
 	add_definitions(-D_LINUX) # It seems enough for all non-Win32 systems
 	add_definitions(-Dstricmp=strcasecmp -Dstrnicmp=strncasecmp -D_snprintf=snprintf -D_vsnprintf=vsnprintf )