Add variant_prepend support for all the properties in bp2build

This is a follow up of aosp/2336916. All the properties that have
variant_prepend tag are supported in bp2build.

Bug: 261644490
Test: TH and modified tests with updated expected behaviors
Change-Id: I13bb5d4d8fcd38bf153fa9083c9c945aec2dfa19
diff --git a/bp2build/configurability.go b/bp2build/configurability.go
index c630965..987c903 100644
--- a/bp2build/configurability.go
+++ b/bp2build/configurability.go
@@ -106,8 +106,9 @@
 
 	return value, []selects{ret}
 }
-func getLabelListValues(list bazel.LabelListAttribute) (reflect.Value, []selects) {
+func getLabelListValues(list bazel.LabelListAttribute) (reflect.Value, []selects, bool) {
 	value := reflect.ValueOf(list.Value.Includes)
+	prepend := list.Prepend
 	var ret []selects
 	for _, axis := range list.SortedConfigurationAxes() {
 		configToLabels := list.ConfigurableValues[axis]
@@ -133,7 +134,7 @@
 		}
 	}
 
-	return value, ret
+	return value, ret, prepend
 }
 
 func labelListSelectValue(selectKey string, list bazel.LabelList, emitEmptyList bool) (bool, reflect.Value) {
@@ -173,7 +174,7 @@
 		value, configurableAttrs, prepend = getStringListValues(list)
 		defaultSelectValue = &emptyBazelList
 	case bazel.LabelListAttribute:
-		value, configurableAttrs = getLabelListValues(list)
+		value, configurableAttrs, prepend = getLabelListValues(list)
 		emitZeroValues = list.EmitEmptyList
 		defaultSelectValue = &emptyBazelList
 		if list.ForceSpecifyEmptyList && (!value.IsNil() || list.HasConfigurableValues()) {