SPIRV-Tools and tests: Update to location-validation in SPIRV-Tools.

This introduces five new "Validation failures":
- baseResults/hlsl.semantic.vert: issue with gl_ClipDistance/CullDistance
- baseResults/spv.430.vert: issue gl_ClipDistance
- baseResults/spv.450.tesc: still unknown
- baseResults/spv.dataOut.frag: gl_FragData should not be supported, problem with front end
- baseResults/spv.meshShaderPerViewUserDefined.mesh: seems okay, maybe a problem with SPIRV-Tools

known_good.json

@@ -5,7 +5,7 @@
       "site" : "github",
       "subrepo" : "KhronosGroup/SPIRV-Tools",
       "subdir" : "External/spirv-tools",
-      "commit" : "e128ab0d624ce7beb08eb9656bb260c597a46d0a"
+      "commit" : "a1fb255a2a6856bba1e5a8486469ac93fca518c2"
     },
     {
       "name" : "spirv-tools/external/spirv-headers",