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/java/platform_compat_config.go b/java/platform_compat_config.go
index 0c973c5..23ba2b0 100644
--- a/java/platform_compat_config.go
+++ b/java/platform_compat_config.go
@@ -78,7 +78,7 @@
 		Include:    "$(BUILD_PREBUILT)",
 		ExtraEntries: []android.AndroidMkExtraEntriesFunc{
 			func(entries *android.AndroidMkEntries) {
-				entries.SetString("LOCAL_MODULE_PATH", "$(OUT_DIR)/"+p.installDirPath.RelPathString())
+				entries.SetString("LOCAL_MODULE_PATH", p.installDirPath.ToMakePath().String())
 				entries.SetString("LOCAL_INSTALLED_MODULE_STEM", p.configFile.Base())
 			},
 		},