SPV: Add SPIRV-Tools validator. This needs the latest SPIR-Tools.

Test/baseResults/hlsl.coverage.frag.out

@@ -117,6 +117,10 @@ gl_FragCoord origin is upper left
 0:?     '@entryPointOutput.nCoverageMask' ( out 1-element array of uint SampleMaskIn)
 0:?     '@entryPointOutput.vColor' (layout( location=0) out 4-component vector of float)
 
+error: SPIRV-Tools Validation Errors
+error: Input variable id <34> is used by entry point 'main' id <4>, but is not listed as an interface
+  %i_1 = OpVariable %_ptr_Input_PS_INPUT Input
+
 // Module Version 10000
 // Generated by (magic number): 80007
 // Id's are bound by 52