--- ./third_party/heimdal/include/heim_threads.h_orig	2023-01-20 08:50:14.182368006 +0000
+++ ./third_party/heimdal/include/heim_threads.h	2023-01-20 08:49:48.890330304 +0000
@@ -54,7 +54,7 @@
 
 #else
 
-#if defined(__clang__) || defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__clang__) || defined(__GNUC__) || defined(__SUNPRO_C) || defined(__xlc__)
 #define HEIMDAL_THREAD_LOCAL __thread
 #else
 #error "thread-local attribute not defined for your compiler"