* Sync with bgfx upstream revision b91d0b6
* Sync with bx upstream revision d60912b
* Sync with bimg upstream revision bd81f60
* Add astc-codec decoder
* Rename VertexDecl to VertexLayout
* Rename UniformType enum Int1 to Sampler.
* Add NVN stub
* Fix unused-const-variable error on macOS
* Drop redundant explicit language parameters
buildoptions_cpp are only applied to c++ files and buildoptions_objcpp are only
applied to objective c++ files. As such, hardcoding -x offers no benefit while
preventing overrides (such as one needed by 3rdparty/bgfx/src/renderer_vk.cpp on
macOS) from working.
* Re-introduce -x c++ in places where C code is compiled as C++ to prevent clang from throwing a warning
* Build bgfx as Objective-C++ on macOS
It is needed due to included headers
* Enable Direct3D12 and Vulkan bgfx rendering backends
* Enable building of spirv shaders
* Properly escape /c in cmd call
* Comment out dx12 bgfx renderer
* Honor VERBOSE setting during shaders build
* Only invert hlsl shader XYZ_TO_sRGB matrix for opengl
* Add spirv shaders
* OpenGL ES needs transposed matrix too
* Metal needs transposed matrix as well
