diff --git a/android/paths.go b/android/paths.go
index 2c50104..6c3009f 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -16,7 +16,6 @@
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -2099,13 +2098,16 @@
 
 // Writes a file to the output directory.  Attempting to write directly to the output directory
 // will fail due to the sandbox of the soong_build process.
+// Only writes the file if the file doesn't exist or if it has different contents, to prevent
+// updating the timestamp if no changes would be made. (This is better for incremental
+// performance.)
 func WriteFileToOutputDir(path WritablePath, data []byte, perm os.FileMode) error {
 	absPath := absolutePath(path.String())
 	err := os.MkdirAll(filepath.Dir(absPath), 0777)
 	if err != nil {
 		return err
 	}
-	return ioutil.WriteFile(absPath, data, perm)
+	return pathtools.WriteFileIfChanged(absPath, data, perm)
 }
 
 func RemoveAllOutputDir(path WritablePath) error {
diff --git a/bp2build/symlink_forest.go b/bp2build/symlink_forest.go
index 183eb12..aac5e7d 100644
--- a/bp2build/symlink_forest.go
+++ b/bp2build/symlink_forest.go
@@ -25,6 +25,7 @@
 	"sync/atomic"
 
 	"android/soong/shared"
+	"github.com/google/blueprint/pathtools"
 )
 
 // A tree structure that describes what to do at each directory in the created
@@ -116,25 +117,13 @@
 		generatedBuildFileContent = packageDefaultVisibilityRegex.ReplaceAll(generatedBuildFileContent, []byte{})
 	}
 
-	outFile, err := os.Create(output)
-	if err != nil {
-		return err
+	newContents := generatedBuildFileContent
+	if newContents[len(newContents)-1] != '\n' {
+		newContents = append(newContents, '\n')
 	}
+	newContents = append(newContents, srcBuildFileContent...)
 
-	_, err = outFile.Write(generatedBuildFileContent)
-	if err != nil {
-		return err
-	}
-
-	if generatedBuildFileContent[len(generatedBuildFileContent)-1] != '\n' {
-		_, err = outFile.WriteString("\n")
-		if err != nil {
-			return err
-		}
-	}
-
-	_, err = outFile.Write(srcBuildFileContent)
-	return err
+	return pathtools.WriteFileIfChanged(output, newContents, 0666)
 }
 
 // Calls readdir() and returns it as a map from the basename of the files in dir