Revert "compiler.h: Raise minimum version of GCC to 5.1 for arm64"

This reverts commit 6eedcd63891e6cd11a9fda55763b69a0ec3b2d43.

Google is still using an antique version of gcc (4.9.2), at least for
build tests. Even though that may generate bad code, we still have to
use it.

BUG=b:178814072
TEST=Build arm64 image with gcc 4.9.2

Signed-off-by: Guenter Roeck <groeck@chromium.org>
1 file changed