[CI] C/glib build broken on OS X

[asfimport]

The Travis-CI build fails to find luarocks:
https://travis-ci.org/apache/arrow/jobs/418753219#L2657

+sudo env PKG_CONFIG_PATH=:/usr/local/opt/libffi/lib/pkgconfig luarocks install lgi
env: luarocks: No such file or directory

The command "$TRAVIS_BUILD_DIR/ci/travis_before_script_c_glib.sh" failed and exited with 127 during .

Reporter: Antoine Pitrou / @pitrou
Assignee: Kouhei Sutou / @kou

PRs and other links:

• GitHub Pull Request #2459

_{Note: This issue was originally created as ARROW-3100. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
@kou

[asfimport]

Kouhei Sutou / @kou:
Issue resolved by pull request 2459
#2459