Add ABFS (Android Build Filesystem) configuration option to Soong

Change-Id: Ibbe81004adc67b1212d7e619a35f7425bfee0d72
diff --git a/ui/build/kati.go b/ui/build/kati.go
index d599c99..a0efd2c 100644
--- a/ui/build/kati.go
+++ b/ui/build/kati.go
@@ -84,7 +84,7 @@
 // arguments, and a custom function closure to mutate the environment Kati runs
 // in.
 func runKati(ctx Context, config Config, extraSuffix string, args []string, envFunc func(*Environment)) {
-	executable := config.PrebuiltBuildTool("ckati")
+	executable := config.KatiBin()
 	// cKati arguments.
 	args = append([]string{
 		// Instead of executing commands directly, generate a Ninja file.