checkpkg: mask errors from lib-provides

bsdtar doesn't consider it an error when your --include doesn't match
anything in the archive, so we're forced to dump stderr to /dev/null
here.

Fixes: https://bugs.archlinux.org/task/42551

checkpkg.in

@@ -63,8 +63,8 @@ for _pkgname in "${pkgname[@]}"; do
 
 	sdiff -s "$TEMPDIR/filelist-$_pkgname-old" "$TEMPDIR/filelist-$_pkgname"
 
-	find-libprovides "$TEMPDIR/$oldpkg" | sort > "$TEMPDIR/libraries-$_pkgname-old"
-	find-libprovides "$pkgfile" | sort > "$TEMPDIR/libraries-$_pkgname"
+	find-libprovides "$TEMPDIR/$oldpkg" 2>/dev/null | sort > "$TEMPDIR/libraries-$_pkgname-old"
+	find-libprovides "$pkgfile" 2>/dev/null | sort > "$TEMPDIR/libraries-$_pkgname"
 	if ! diff_output="$(sdiff -s "$TEMPDIR/libraries-$_pkgname-old" "$TEMPDIR/libraries-$_pkgname")"; then
 		msg "Sonames differ in $_pkgname!"
 		echo "$diff_output"