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_qt/CMakeLists.txt

@@ -164,6 +164,7 @@ add_executable(citra-qt
     multiplayer/state.cpp
     multiplayer/state.h
     multiplayer/validation.h
+    precompiled_headers.h
     uisettings.cpp
     uisettings.h
     qt_image_interface.cpp
@@ -319,3 +320,7 @@ if (MSVC)
         copy_citra_FFmpeg_deps(citra-qt)
     endif()
 endif()
+
+if (CITRA_USE_PRECOMPILED_HEADERS)
+    target_precompile_headers(citra-qt PRIVATE precompiled_headers.h)
+endif()

src/citra_qt/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"