Support ASAN for ckati and ninja

I missed this when converting to soong_ui.

Test: m -j blueprint_tools (check soong.log)
Test: SANITIZE_HOST=address m -j blueprint_tools
Change-Id: I01eb567db6848dc36dd679557291a4e600a63bba
diff --git a/ui/build/ninja.go b/ui/build/ninja.go
index 33f9a07..054af24 100644
--- a/ui/build/ninja.go
+++ b/ui/build/ninja.go
@@ -26,7 +26,7 @@
 	ctx.BeginTrace("ninja")
 	defer ctx.EndTrace()
 
-	executable := "prebuilts/build-tools/" + config.HostPrebuiltTag() + "/bin/ninja"
+	executable := config.PrebuiltBuildTool("ninja")
 	args := []string{
 		"-d", "keepdepfile",
 	}