[llvm-objcopy][test] Add a test to show that argv[0] is included in error/warning messages

test/llvm-objcopy/ELF/error-format.test is similar to test/llvm-readobj/error-format.test added in D66425.

Reviewed By: grimar, jhenderson

Differential Revision: https://reviews.llvm.org/D66476

llvm-svn: 369392