envsetup: add reposync function

 - using repo sync command w/ cat function to decypher user's system core count for jobs parameter

derived from drewis @CM

Change-Id: Ia97fa7029c63cf9470d43780d0da2f907e986ba2

Conflicts:
	envsetup.sh

Change-Id: Ia97fa7029c63cf9470d43780d0da2f907e986ba2
Merge "envsetup: add reposync function" into lollipop