-mglobal-merge is translated to the appropriate backend option in
the driver. r277322 changed the AArch64 option name in the backend,
but the driver was never updated.
llvm-svn: 292192
Follow-up to r234666. With this, the -m[no-]global-merge options
have the expected behavior. Previously, -mglobal-merge was ignored,
and there was no way of enabling the optimization.
llvm-svn: 234668