gn2bp: Update not to change Android.bp.swp every run

Order of set iteration is not the same everytime.
Sort before the iteration to make Android.bp.swp same every time we run
update_result.sh

Test: ./update_result.sh

Change-Id: Ie6495db1b2ad62113ba4fccb5d76d6590a91a5ba
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 7487287..b616db1 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -706,7 +706,7 @@
   So each source file will generate an output whose name is the {source_name-reversed-inc.cc}
   """
   new_args = []
-  for i, src in enumerate(target.sources):
+  for i, src in enumerate(sorted(target.sources)):
     # don't add script arg for the first source -- create_action_module
     # already does this.
     if i != 0: