8149479: Fix compare.sh to have a clean baseline with COMPARE_BUILD
Reviewed-by: ihse, tbell
os_family = aix
arch = ppc
arch_model = ppc_64
os_arch = aix_ppc
os_arch_model = aix_ppc_64
lib_arch = ppc64
compiler = xlc
gnu_dis_arch = ppc64
sysdefs = -DAIX -DPPC64