[dxvk] Add pass to check whether a shader has spec constants

Pipeline libraries cannot be used for shaders with user spec constants.

src/dxvk/dxvk_shader.cpp

@@ -115,6 +115,9 @@ namespace dxvk {
           bindingOffsets[varId].setOffset = ins.offset() + 3;
         }
 
+        if (ins.arg(2) == spv::DecorationSpecId && ins.arg(3) < MaxNumSpecConstants)
+          m_flags.set(DxvkShaderFlag::HasSpecConstants);
+
         if (ins.arg(2) == spv::DecorationLocation && ins.arg(3) == 1) {
           m_o1LocOffset = ins.offset() + 3;
           o1VarId = ins.arg(1);

src/dxvk/dxvk_shader.h

@@ -39,6 +39,7 @@ namespace dxvk {
   enum DxvkShaderFlag : uint64_t {
     HasSampleRateShading,
     HasTransformFeedback,
+    HasSpecConstants,
     ExportsStencilRef,
     ExportsViewportIndexLayerFromVertexStage,
   };