makepkg: when signing packages, report package filename on failure

In commit c6b04c0465 the signing function
was moved out of fakeroot, and thus out of the create_package loop. This
meant that if package signing failed, it was no longer possible to tell
which package it failed on by checking which package creation is
currently running. Successful signing attempts do not have this problem
as we already printed the name of the signature file.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/libmakepkg/integrity/generate_signature.sh.in

@@ -40,7 +40,7 @@ create_signature() {
 	if (( ! ret )); then
 		msg2 "$(gettext "Created signature file %s.")" "${filename##*/}.sig"
 	else
-		warning "$(gettext "Failed to sign package file.")"
+		warning "$(gettext "Failed to sign package file %s.")" "${filename##*/}"
 	fi
 
 	return $ret