Use AtomicOutput in process_native_prebuilt.py

eu-strip's output keeps mode from source file which might not be
writable thus it fails to override its output on the next run.
AtomicOutput fixes the issue. Also it is good practice anyways.

Change-Id: I7b3574dac55cc44e6d0572704f26e42969331ddc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2458786
Auto-Submit: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Reviewed-by: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814841}

build/android/gyp/process_native_prebuilt.py

@@ -20,14 +20,17 @@ def main(args):
   parser.add_argument('--unstripped-output-path', required=True, help='')
   options = parser.parse_args(args)
 
-  cmd = [
-      options.strip_path,
-      options.input_path,
-      '-o',
-      options.stripped_output_path,
-  ]
-
-  build_utils.CheckOutput(cmd)
+  # eu-strip's output keeps mode from source file which might not be writable
+  # thus it fails to override its output on the next run. AtomicOutput fixes
+  # the issue.
+  with build_utils.AtomicOutput(options.stripped_output_path) as out:
+    cmd = [
+        options.strip_path,
+        options.input_path,
+        '-o',
+        out.name,
+    ]
+    build_utils.CheckOutput(cmd)
   shutil.copyfile(options.input_path, options.unstripped_output_path)