Port yuzu-emu/yuzu#9300: "CMake: Use precompiled headers to improve compile times" (#6213)

Co-authored-by: Ameer J <52414509+ameerj@users.noreply.github.com>

src/citra/CMakeLists.txt

@@ -10,6 +10,7 @@ add_executable(citra
     emu_window/emu_window_sdl2.h
     lodepng_image_interface.cpp
     lodepng_image_interface.h
+    precompiled_headers.h
     resource.h
 )
 
@@ -30,3 +31,7 @@ if (MSVC)
     include(CopyCitraSDLDeps)
     copy_citra_SDL_deps(citra)
 endif()
+
+if (CITRA_USE_PRECOMPILED_HEADERS)
+    target_precompile_headers(citra PRIVATE precompiled_headers.h)
+endif()

src/citra/precompiled_headers.h

@@ -0,0 +1,7 @@
+// Copyright 2022 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_precompiled_headers.h"