Convert disting of api txt from mk to bp

droidstubs dist now dists the api file, so convert these manual
mk rules into bp dist instead.

Bug: 149293194
Test: m dist sdk && find out/dist/apistubs -name /android\.txt
Change-Id: I96052b427dc01a6d24b040ad0006129d4d1e48fb
diff --git a/services/Android.bp b/services/Android.bp
index 490481c..52c5993 100644
--- a/services/Android.bp
+++ b/services/Android.bp
@@ -142,6 +142,11 @@
             baseline_file: "api/lint-baseline.txt",
         },
     },
+    dist: {
+        targets: ["sdk", "win_sdk"],
+        dir: "apistubs/android/system-server/api",
+        dest: "android.txt",
+    },
 }
 
 java_library {