Add necessary system packages to accept_keywords for musl compat

profiles/base/package.accept_keywords

+=app-arch/gzip-1.7 **
+=app-arch/pax-20160306 **
 =dev-util/cflow-1.4 **
+=sys-apps/less-483-r1 **
 =sys-apps/shadow-4.2.1-r2 **
 =sys-devel/m4-1.4.17 **
 =sys-kernel/linux-headers-4.4 **