Add default descriptorset decoration for acceleration structure (#2257)

variables.

SPIRV/GlslangToSpv.cpp

@@ -1292,7 +1292,8 @@ bool IsDescriptorResource(const glslang::TType& type)
     // basically samplerXXX/subpass/sampler/texture are all included
     // if they are the global-scope-class, not the function parameter
     // (or local, if they ever exist) class.
-    if (type.getBasicType() == glslang::EbtSampler)
+    if (type.getBasicType() == glslang::EbtSampler ||
+        type.getBasicType() == glslang::EbtAccStruct)
         return type.getQualifier().isUniformOrBuffer();
 
     // None of the above.