Replace android.WriteFile rule with android.WriteFileRule

The android.WriteFile rule takes careful escaping to produce the
right contents.  Wrap it in an android.WriteFileRule that handles
the escaping.

Test: compare all android.WriteFile outputs
Change-Id: If71a5843af47a37ca61714e1a1ebb32d08536c31
diff --git a/dexpreopt/config.go b/dexpreopt/config.go
index 03accc8..f77246e 100644
--- a/dexpreopt/config.go
+++ b/dexpreopt/config.go
@@ -488,13 +488,7 @@
 		return
 	}
 
-	ctx.Build(pctx, android.BuildParams{
-		Rule:   android.WriteFile,
-		Output: android.PathForOutput(ctx, "dexpreopt_soong.config"),
-		Args: map[string]string{
-			"content": string(data),
-		},
-	})
+	android.WriteFileRule(ctx, android.PathForOutput(ctx, "dexpreopt_soong.config"), string(data))
 }
 
 func (s *globalSoongConfigSingleton) MakeVars(ctx android.MakeVarsContext) {