When objcopy encounters an already-present section, adding the new
debuglink will fail with a warning. Remove any existing `.gnu_debuglink`
section to work around this problem.
Arch Linux's `rust` package is affected by this. Apparently when LLVM's
LLD links in `/usr/lib/Scrt1.o` it will also copy the `.gnu_debuglink`
section.
See: https://bugs.gentoo.org/787623