Revert "Revert "UPSTREAM: efi/libstub/arm64: Set -fpie when building the EFI stub""

In isolation, the original change will break building efistub for ARM64
with gcc.  This wasn't an issue upstream due to the earlier change
60f38de7a8d4 ("efi/libstub: Unify command line param parsing").  That's
now been backported to AOSP too.

This reverts commit 89805266.

Change-Id: I44eff2d17809b18181e2084abaf129ca4e2eb8d6
Signed-off-by: Greg Hackmann <ghackmann@google.com>