product_variables srcs in prebuilt_etc

bp2build conversion handles product_variable srcs

bug: 228353067
Test: prebuilt_etc_conversion_test.go
Change-Id: I82d3a384ee14d4e981d502dd9eb824c87d5ae2c7
diff --git a/bazel/properties.go b/bazel/properties.go
index d82fa64..11f6247 100644
--- a/bazel/properties.go
+++ b/bazel/properties.go
@@ -309,7 +309,19 @@
 	_, containsProductVariables := axisTypes[productVariables]
 	if containsProductVariables {
 		if containsOs || containsArch || containsOsArch {
-			return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+			if containsArch {
+				allProductVariablesAreArchVariant := true
+				for k := range la.ConfigurableValues {
+					if k.configurationType == productVariables && k.outerAxisType != arch {
+						allProductVariablesAreArchVariant = false
+					}
+				}
+				if !allProductVariablesAreArchVariant {
+					return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+				}
+			} else {
+				return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+			}
 		}
 	}
 	if (containsOs && containsArch) || (containsOsArch && (containsOs || containsArch)) {