Add mac_tool.py from gyp 0bb67471bca068996e15b56738fa4824dfa19de0

Add mac_tool.py from gyp 0bb67471bca068996e15b56738fa4824dfa19de0

This script is used by the mac build for compiling targets on the host.
It comes from the gyp repo, but is a standalone script independent of
the rest of gyp. This adds the file in the path that the build files
expect it to live in to avoid needing to modify those build rules.

R=cstout@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/7f2dde3f8109dd376cedaa38e8e5fd94bc240616

[jamesr, 2015-05-06 18:22:11]

jamesr@chromium.org changed reviewers:
+ cstout@chromium.org

[cdotstout, 2015-05-06 18:29:21]

lgtm

[jamesr, 2015-05-06 18:31:33]

Committed patchset #1 (id:1) manually as
7f2dde3f8109dd376cedaa38e8e5fd94bc240616 (presubmit successful).