Add ABFS (Android Build Filesystem) configuration option to Soong

Change-Id: Ibbe81004adc67b1212d7e619a35f7425bfee0d72
diff --git a/ui/build/soong.go b/ui/build/soong.go
index e18cc25..2ccdfec 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -661,7 +661,7 @@
 		}
 
 		ninjaArgs = append(ninjaArgs, targets...)
-		ninjaCmd := config.PrebuiltBuildTool("ninja")
+		ninjaCmd := config.NinjaBin()
 		if config.useN2 {
 			ninjaCmd = config.PrebuiltBuildTool("n2")
 		}