editors/emacs-devel: disable NATIVECOMP on powerpc* to fix build and reenable clang builds

Backtrace:
0x1016e5d8 <emacs_backtrace+0x78> at /wrkdirs/usr/ports/editors/emacs-devel/work-full/emacs-75e3ea04239/src/emacs
0x100244e0 <terminate_due_to_signal+0xcc> at /wrkdirs/usr/ports/editors/emacs-devel/work-full/emacs-75e3ea04239/src/emacs
0x100247e8 <handle_fatal_signal+0x1c> at /wrkdirs/usr/ports/editors/emacs-devel/work-full/emacs-75e3ea04239/src/emacs
0x1016b258 <deliver_thread_signal.constprop.0+0x58> at /wrkdirs/usr/ports/editors/emacs-devel/work-full/emacs-75e3ea04239/src/emacs
0x1016b320 <handle_sigsegv+0x60> at /wrkdirs/usr/ports/editors/emacs-devel/work-full/emacs-75e3ea04239/src/emacs
0x812a66128 <pthread_sigmask+0x8e4> at /lib/libthr.so.3