build: Make AM_PROG_AR conditional
build: Make AM_PROG_AR conditional

AM_PROG_AR is not available in earlier versions of Automake.
Make the flag conditional on whether it is available or not.

Signed-off-by: Robert Love <ae32029cc3b561e3768d1db8669e99f5bdf25e4b@intel.com>

cleech/libhbalinux,cleech/libhbalinux