Use WriteFileRule instead of custom echo commands

These instances could use WriteFileRule instead of
making their own shell code to write a file.

Test: Presubmits
Change-Id: I9c809b2164a68b4ce1c22fbbd0d7497240110b39
diff --git a/android/buildinfo_prop.go b/android/buildinfo_prop.go
index acebdbb..46f6488 100644
--- a/android/buildinfo_prop.go
+++ b/android/buildinfo_prop.go
@@ -61,11 +61,10 @@
 		return
 	}
 
-	rule := NewRuleBuilder(pctx, ctx)
-	cmd := rule.Command().Text("(")
+	lines := make([]string, 0)
 
 	writeString := func(str string) {
-		cmd.Text(`echo "` + str + `" && `)
+		lines = append(lines, str)
 	}
 
 	writeString("# begin build properties")
@@ -142,8 +141,7 @@
 
 	writeString("# end build properties")
 
-	cmd.Text("true) > ").Output(p.outputFilePath)
-	rule.Build("build.prop", "generating build.prop")
+	WriteFileRule(ctx, p.outputFilePath, strings.Join(lines, "\n"))
 
 	if !p.installable() {
 		p.SkipInstall()