graphics: route compact color exports through CB_SHADER_MASK

src/graphics/shader/shaderPixelParameter.cpp

@@ -11,6 +11,19 @@ constexpr uint32_t PsInputFlatShade  = 0x00000400u;
 
 } // namespace
 
+uint32_t ShaderPixelExportTarget(uint32_t shader_mask, uint32_t export_index) {
+	for (uint32_t target = 0; target < 8u; target++) {
+		if (((shader_mask >> (target * 4u)) & 0xfu) == 0u) {
+			continue;
+		}
+		if (export_index == 0u) {
+			return target;
+		}
+		export_index--;
+	}
+	return UINT32_MAX;
+}
+
 uint32_t ShaderPixelParameterMappedLocation(const ShaderPixelInputInfo& info, uint32_t input) {
 	return input < info.input_num ? info.interpolator_settings[input] & PsInputOffsetMask : input;
 }