Replace RelPathString() with ToMakePath()

Add a ToMakePath() method that returns a new path that points out
out/ instead of out/soong/, and replace the
"$(OUT_DIR)/" + path.RelPathString()
pattern with
path.ToMakePath().String()

Bug: 141877526
Test: m checkbuild
Change-Id: I391b9f2ed78c83a58d905d48355ce9b01d610d16
diff --git a/rust/androidmk.go b/rust/androidmk.go
index 107959f..a6208db 100644
--- a/rust/androidmk.go
+++ b/rust/androidmk.go
@@ -116,11 +116,10 @@
 		ret.OutputFile = android.OptionalPathForPath(compiler.path)
 	}
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
-		path := compiler.path.RelPathString()
-		dir, file := filepath.Split(path)
+		path, file := filepath.Split(compiler.path.ToMakePath().String())
 		stem, suffix, _ := android.SplitFileExt(file)
 		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+suffix)
-		fmt.Fprintln(w, "LOCAL_MODULE_PATH := $(OUT_DIR)/"+filepath.Clean(dir))
+		fmt.Fprintln(w, "LOCAL_MODULE_PATH := "+path)
 		fmt.Fprintln(w, "LOCAL_MODULE_STEM := "+stem)
 	})
 }