Incorrect validation of DebugTypePointer: non-trivial base types are not allowed

[RodrigoCastiel]

When validating DebugTypePointer instructions, the base type is checked to be a trivial type defined by DebugTypeBasic. This means that pointers to vectors or matrices are considered invalid, which prevents variables such as vec4 fragColor (GLSL) to have debug info emitted.

SPIRV-Tools/source/val/validate_extensions.cpp

Lines 3170 to 3177 in 933db56

	case CommonDebugInfoDebugTypePointer: {
	auto validate_base_type =
	ValidateOperandBaseType(_, inst, 5, ext_inst_name);
	if (validate_base_type != SPV_SUCCESS) return validate_base_type;
	CHECK_CONST_UINT_OPERAND("Storage Class", 6);
	CHECK_CONST_UINT_OPERAND("Flags", 7);
	break;
	}

This validation rule is not present in the NonSemantic.Shader.DebugInfo.100 specification. Potential solutions:
(1) Check that Base Type in DebugTypePointer could be any debug type instruction.
(2) Simply remove the validation - ValidateOperandBaseType(_, inst, 5, ext_inst_name)
(3) Update the specification to reflect the intended behaviour in case pointers to non-trivial types are not allowed

Thanks for reading and checking that!