Add support in Metal and Vulkan for [earlydepthstencil] (#2764)

src/bgfx_shader.sh

@@ -22,7 +22,7 @@
 #	define UNROLL
 #endif // BGFX_SHADER_LANGUAGE_HLSL > 300
 
-#if BGFX_SHADER_LANGUAGE_HLSL > 300 && BGFX_SHADER_TYPE_FRAGMENT
+#if (BGFX_SHADER_LANGUAGE_HLSL > 300 || BGFX_SHADER_LANGUAGE_METAL || BGFX_SHADER_LANGUAGE_SPIRV) && BGFX_SHADER_TYPE_FRAGMENT
 #	define EARLY_DEPTH_STENCIL [earlydepthstencil]
 #else
 #	define EARLY_DEPTH_STENCIL