Remove unused parts of the strip implementation.

The --use-gnu-strip option was removed from the shell script already,
and it no longer uses the $CROSS_COMPILE environment variable.

Bug: http://b/185257607
Bug: http://b/147452927
Test: treehugger
Change-Id: If9f7b75d52c1e9cd167d73eeba8f77054ffd63a7