build: Aggregate CyanogenMod copyright notices

Join and format copyright notices specifically identified as
being from the CyanogenMod project (by presence of a NOTICE.cm
file).

ATTENTION: As copyright holders to the CM modifications, the
CyanogenMod Project kindly requests that you do _NOT_ remove the
aggregation, display, or NOTICE.cm files themselves from your
source tree if you are distributing a derivative of the CyanogenMod
Android distribution, or any component of CM (including device
configuration trees)

Change-Id: I28b6df002e05671f6df3a5d378b57b03bf912a39