See webkit_layout_tests failure in
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/fuchsia_x64/21853

4957 2018-05-16 23:01:36.077 E: internal failure: [Errno 13] Permission denied: '/b/s/w/ir/third_party/fuchsia-sdk/sdk/qemu/bin/ivshmem-client'
Traceback (most recent call last):
  File "/b/s/swarming_bot.1.zip/client/run_isolated.py", line 688, in map_and_run
    use_symlinks=data.use_symlinks)
  File "/b/s/swarming_bot.1.zip/client/run_isolated.py", line 483, in fetch_and_map
    use_symlinks=use_symlinks)
  File "/b/s/swarming_bot.1.zip/client/isolateserver.py", line 1809, in fetch_isolated
    putfile(ifd, fp, file_mode, ti.size)
  File "/b/s/swarming_bot.1.zip/client/isolateserver.py", line 250, in putfile
    with fs.open(dstpath, 'wb') as dstfileobj:
  File "/b/s/swarming_bot.1.zip/utils/fs.py", line 234, in open
    return __builtin__.open(extend(path), *args, **kwargs)
IOError: [Errno 13] Permission denied: '/b/s/w/ir/third_party/fuchsia-sdk/sdk/qemu/bin/ivshmem-client'
Sending the crash report ... done.

As far as I can tell this happens because webkit_layout_tests depends on 2 Fuchsia targets: //content/shell:content_shell_fuchsia and //build/fuchsia/layout_test_proxy:layout_test_proxy_runner and both of these targets have //third_party/fuchsia-sdk/sdk in runtime_deps . Some files in the sdk dir have r-x permissions, i.e. they are not writable. As result the script fails to write them when trying to write second duplicate of these files.