https://github.com/hunspell/hyphen/commit/3d05509b7ce8c350f4476830b00241025eeae329
https://github.com/hunspell/hyphen/pull/12

From 3d05509b7ce8c350f4476830b00241025eeae329 Mon Sep 17 00:00:00 2001
From: Philip Chimento <philip.chimento@gmail.com>
Date: Sat, 12 Nov 2016 00:36:06 -0800
Subject: [PATCH] More portable awk script

gensub() is specific to gawk, this uses gsub() instead in order to build
on platforms that don't have gawk such as macOS.
---
 lig.awk | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/lig.awk b/lig.awk
index 6737170..4ea5e46 100644
--- a/lig.awk
+++ b/lig.awk
@@ -24,14 +24,20 @@ c=b
 c!=b { print c }
 
 /f[1-9]?$/ {
-	print gensub("f[1-9]?$", "ff", "g", b);
-	if (c!=b) print gensub("f[1-9]?$", "ff", "g", c);
-
-	print gensub("f[1-9]?$", "fi", "g", b);
-	if (c!=b) print gensub("f[1-9]?$", "fi", "g", c);
-
-	print gensub("f[1-9]?$", "fl", "g", b);
-	if (c!=b) print gensub("f[1-9]?$", "fl", "g", c);
+	out=b; gsub("f[1-9]?$", "ff", out); print out
+	if (c!=b) {
+		out=c; gsub("f[1-9]?$", "ff", out); print out
+	}
+
+	out=b; gsub("f[1-9]?$", "fi", out); print out
+	if (c!=b) {
+		out=c; gsub("f[1-9]?$", "fi", out); print out
+	}
+
+	out=b; gsub("f[1-9]?$", "fl", out); print out
+	if (c!=b) {
+		out=c; gsub("f[1-9]?$", "fl", out); print out
+	}
 }