Don't build otapackage on Mac.
Don't build otapackage on Mac.

Also removed the unneeded variable DISTTOOLS
and the unnecessary dependency of otapackage/updatepackage on DISTTOOLS.

Bug: 23085297
Change-Id: I6b269003a72bb48eda1260c8d9b4bd88974bcde9

xorware/android_build,xorware/android_build,xorware/android_build,xorware/android_build,xorware/android_build