Add -Wl,-maarch64linux

The "-maarch64linux" switch is needed before aarch64-*4.8 is rebuilt with
backport of upstream patch, see https://android-review.googlesource.com/#/c/91099/

The existing ld.bfd is fine because it's configured to support
aarch64linux only.  ld.mcld (see https://android-review.googlesource.com/#/c/91047)
needs explicit emulation switch because it supports multiple targets

Change-Id: Idc1a491c5722ea9e26db917b667b1000bccc1f60