Don't try to create a lib64 symlink.
https://github.com/irstlm-team/irstlm/issues/27
--- src/CMakeLists.txt.orig	2015-12-09 17:31:15.000000000 -0600
+++ src/CMakeLists.txt	2023-02-05 21:21:32.000000000 -0600
@@ -82,3 +82,2 @@
 
-add_custom_target(LinkToLib64 ALL DEPENDS LNS)