Added metal-cpp to the project

Raw header file from Metal-cpp project
Generated using

./SingleHeader/MakeSingleHeader.py Foundation/Foundation.hpp QuartzCore/QuartzCore.hpp Metal/Metal.hpp

Metal-cpp project: https://developer.apple.com/metal/cpp/
https://developer.apple.com/metal/cpp/files/metal-cpp_macOS12_iOS15.zip

renderdoc/driver/metal/CMakeLists.txt

@@ -1,4 +1,6 @@
-set(sources )
+set(sources
+    official/metal-cpp.h
+    official/metal-cpp.cpp)
 
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
 add_library(rdoc_metal OBJECT ${sources})

renderdoc/driver/metal/official/metal-cpp.cpp

@@ -0,0 +1,33 @@
+/******************************************************************************
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019-2022 Baldur Karlsson
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ ******************************************************************************/
+
+// Metal-cpp project: https://developer.apple.com/metal/cpp/
+// https://developer.apple.com/metal/cpp/files/metal-cpp_macOS12_iOS15.zip
+
+#define NS_PRIVATE_IMPLEMENTATION
+#define CA_PRIVATE_IMPLEMENTATION
+#define MTL_PRIVATE_IMPLEMENTATION
+
+#include "metal-cpp.h"
+