[cmake] Reduce spam on builds for MSVC (#3454)

Fix for disable-warning-as-error flags set for MSVC not CLANG dripping into externals and causing override warnings on Ninja (cl)

Signed-off-by: xbzk <xbzk@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3454
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: Maufeat <sahyno1996@gmail.com>
Co-authored-by: xbzk <xbzk@eden-emu.dev>
Co-committed-by: xbzk <xbzk@eden-emu.dev>

CMakeLists.txt

@@ -178,7 +178,9 @@ endif()
 
 # Disable Warnings as Errors for MSVC
 if (MSVC AND NOT CXX_CLANG)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W3 /WX-")
+    # This was dripping into spirv, being overriden, and causing cl flag override warning
+    # set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W3 /WX-")
+    set(CMAKE_CXX_FLAGS_INIT "${CMAKE_CXX_FLAGS_INIT} /W3 /WX-")
 endif()
 
 # Set bundled sdl2/qt as dependent options.