https://github.com/abseil/abseil-cpp/issues/1825

--- abseil-cpp-20250127.1/absl/time/clock_test.cc.orig
+++ abseil-cpp-20250127.1/absl/time/clock_test.cc
@@ -18,7 +18,7 @@
 #if defined(ABSL_HAVE_ALARM)
 #include <signal.h>
 #include <unistd.h>
-#ifdef _AIX
+#if defined(_AIX) || defined(__illumos__)
 // sig_t is not defined in AIX.
 typedef void (*sig_t)(int);
 #endif