As with probably many other systems I don't have gawk installed by default. So I propose to add a check similar to the following patch. It might be worth to include other variants like nawk - assuming that there are no special features needed. At least here it seemed to work fine.
--- src/tools/affixcompress (Revision 20487)
+++ src/tools/affixcompress (Arbeitskopie)
LC_ALL=C sort word_list >sorted_word_list
affixcompress sorted_word_list [max_affix_rules]
@@ -21,7 +21,11 @@
+if which gawk; then