Output json without trailing whitespaces but with trailing newlines.

Makes them more editor friendly, primarily when copied into
system/linkerconfig/testdata/root.

Test: m
Test: No diff between apex_manifest_full.json in out/
  and in linkerconfig/testdata/root/
Bug: 140599044
Change-Id: I6dacdd4baa59e6d70586c4a6343b9b8fd1b574f6

scripts/jsonmodify.py

@@ -112,9 +112,10 @@ def main():
 
   if args.out:
     with open(args.out, "w") as f:
-      json.dump(obj, f, indent=2)
+      json.dump(obj, f, indent=2, separators=(',', ': '))
+      f.write('\n')
   else:
-    print(json.dumps(obj, indent=2))
+    print(json.dumps(obj, indent=2, separators=(',', ': ')))
 
 
 if __name__ == '__main__':