Factor out some of the makefile cruft.

I really don't want to add yet another copy for aarch64.

Also sort arm, mips, and x86.

Also silence the "TARGET_ARCH_VARIANT" warning for non-ARM; Intel and MIPS
have both complained about it.

Change-Id: I32c592a90c0cf0cdae250d84035b3e4655543781
1 file changed