strip: Overwrite debuglink when it's already present

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

scripts/libmakepkg/tidy/strip.sh.in

@@ -100,6 +100,7 @@ collect_debug_symbols() {
 			return
 		fi
 
+		safe_objcopy "$binary" --remove-section=.gnu_debuglink
 		safe_objcopy "$binary" --add-gnu-debuglink="$dbgdir/${binary#/}.debug"
 
 		# create any needed hardlinks