Consider GL_EXT_scalar_block_layout when validating SPIR-V

If GL_EXT_scalar_block_layout is requested by the shader, set the
option to allow scalar blocks in the SPIR-V validator.

Fix the existing tests using scalar layout to not expect "Validation
failed".

Fixes #2400.

SPIRV/SpvTools.cpp

@@ -153,6 +153,7 @@ void SpirvToolsValidate(const glslang::TIntermediate& intermediate, std::vector<
     spv_validator_options options = spvValidatorOptionsCreate();
     spvValidatorOptionsSetRelaxBlockLayout(options, intermediate.usingHlslOffsets());
     spvValidatorOptionsSetBeforeHlslLegalization(options, prelegalization);
+    spvValidatorOptionsSetScalarBlockLayout(options, intermediate.usingScalarBlockLayout());
     spvValidateWithOptions(context, options, &binary, &diagnostic);
 
     // report