Externals: Update glslang to 16.0.0 and allow using system glslang

Source/Core/VideoCommon/CMakeLists.txt

@@ -224,7 +224,7 @@ PRIVATE
   xxhash::xxhash
   imgui
   implot
-  glslang
+  glslang::glslang
   tinygltf
 )
 
@@ -267,16 +267,6 @@ if(FFmpeg_FOUND)
   endif()
 endif()
 
-# Silence warnings on glslang by flagging it as a system include
-target_include_directories(videocommon
-SYSTEM PUBLIC
-  ${CMAKE_SOURCE_DIR}/Externals/glslang/glslang/glslang/Public
-SYSTEM PRIVATE
-  ${CMAKE_SOURCE_DIR}/Externals/glslang/glslang/glslang
-  ${CMAKE_SOURCE_DIR}/Externals/glslang/glslang/SPIRV
-  ${CMAKE_SOURCE_DIR}/Externals/glslang/glslang
-)
-
 if(MSVC)
   # Add precompiled header
   target_link_libraries(videocommon PRIVATE use_pch)

Source/Core/VideoCommon/Spirv.cpp

@@ -3,9 +3,8 @@
 
 #include "VideoCommon/Spirv.h"
 
-// glslang includes
-#include "GlslangToSpv.h"
-#include "disassemble.h"
+#include <glslang/SPIRV/GlslangToSpv.h>
+#include <glslang/SPIRV/disassemble.h>
 
 #include "Common/FileUtil.h"
 #include "Common/Logging/Log.h"

Source/Core/VideoCommon/Spirv.h

@@ -8,7 +8,7 @@
 #include <string_view>
 #include <vector>
 
-#include "ShaderLang.h"
+#include <glslang/Public/ShaderLang.h>
 
 #include "Common/CommonTypes.h"
 #include "VideoCommon/VideoCommon.h"