Fix build failure when zcat is not gzcat.
--- link-alternative-names.orig	2012-06-17 13:19:27.000000000 -0500
+++ link-alternative-names	2018-11-05 10:23:25.000000000 -0600
@@ -46,7 +46,7 @@
 }
 
 find_names() {
-    zcat -f "$@" |
+    gzip -dc "$@" |
     sed -n '/^\.SH NAME/,/^\.SH SYNOPSIS/p' |
     grep -v '^\.SH ' |
     tr '\12' ' ' |