Thanks to a recent binutils change which doesn't generate unused
symbols, it's now possible for thunk_64.o be completely empty without
CONFIG_PREEMPTION: no text, no data, no symbols.

We could edit the Makefile to only build that file when
CONFIG_PREEMPTION is enabled, but that will likely create confusion
if/when the thunks end up getting used by some other code again.

Just ignore it and move on.
Reported-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NMiroslav Benes <mbenes@suse.cz>
Tested-by: NNathan Chancellor <natechancellor@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1254Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>