add gcd funtion to envsetup.sh

  gcd - cd to any tracked git project from any other
  path in the build tree.

Change-Id: I8fde827dc51ac4006030712239f9ee6593b07c4c
Support for JCROM
Merge branch 'kitkat-jcrom' of github.com:JCROM-Android/aokp_build into kitkat-jcrom