cm.mk: don't override BUILD_ID

Change-Id: I3a0040ee65cefb25908c9710b324a319a468d5b6
Merge "cm.mk: don't override BUILD_ID" into cm-11.0
Merge remote-tracking branch 'cm/cm-11.0' into HEAD

Conflicts:
	cm.mk

Change-Id: I79612ea6b22d57b98e85b1860970446baa8fa5f1