Add gumbo to common directory locations.
Add gumbo to common directory locations.

Change-Id: Ia7e412e42147b344c304e6857233cfe1a2c64aec
Tested: Gumbo build in flatui works on OSX.

google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil