Doing a 'make clean', 'make distclean', or 'make dist-clean' gets errors
about an invalid shell option: "/bin/sh: 0: Illegal option -".

The clean targets do not include the makeopts file which defines GREP and
LDCONFIG because the file may not exist and the distclean/dist-clean
targets will delete it anyway.

ASTERISK-27715

Change-Id: I33d40acdb03862bc89aeb6fb1ff497894a8ea7f5