objcopy fails silently with an empty input file

[Shaun Jackman]

objcopy silently fails when the input file is empty. I'd rather it
didn't fail -- this used to work in previous versions -- but it
definitely shouldn't fail silently.

Cheers,
Shaun

$ arm-elf-objcopy --version | head -1
GNU objcopy 2.15
$ echo > not-empty
$ arm-elf-objcopy -Ibinary -Oelf32-little not-empty not-empty.o; echo $?
0
$ echo -n > empty
$ arm-elf-objcopy -Ibinary -Oelf32-little empty empty.o; echo $?
1