Add partialcompileclean phony

When SOONG_USE_PARTIAL_COMPILE transitions from on to off, we need to
remove all files that may have been built using partial compile.

Bug: b/396145326
Test: manual, TH
Change-Id: I1d91f95883fd8b1d92731a490244a898f25e614d
diff --git a/android/module.go b/android/module.go
index 80275a3..647dc37 100644
--- a/android/module.go
+++ b/android/module.go
@@ -2997,6 +2997,9 @@
 func (c *buildTargetSingleton) GenerateBuildActions(ctx SingletonContext) {
 	var checkbuildDeps Paths
 
+	// Create a top level partialcompileclean target for modules to add dependencies to.
+	ctx.Phony("partialcompileclean")
+
 	mmTarget := func(dir string) string {
 		return "MODULES-IN-" + strings.Replace(filepath.Clean(dir), "/", "-", -1)
 	}