The thread start routine must return void *, and int and void *
are distinct types.  Compilers increasingly issue errors instead
of warnings for such type errors, and this causes the configure
probe to fail unconditionally, even if the system supports
__thread variables.

Submitted upstream: <https://github.com/mono/mono/pull/21730>

diff --git a/configure.ac b/configure.ac
index bbbd1622d9728859..5a3a5770c8a3cdb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2833,14 +2833,16 @@ if test x$host_win32 = xno; then
 			__thread int i;
 			static int res1, res2;
 
-			void thread_main (void *arg)
+			void *thread_main (void *parg)
 			{
+				int arg = *(int *)parg;
 				i = arg;
 				sleep (1);
 				if (arg == 1)
 					res1 = (i == arg);
 				else
 					res2 = (i == arg);
+				return NULL;
 			}
 
 			int main () {
@@ -2848,8 +2850,10 @@ if test x$host_win32 = xno; then
 
 				i = 5;
 
-				pthread_create (&t1, NULL, thread_main, 1);
-				pthread_create (&t2, NULL, thread_main, 2);
+				int one = 1;
+				pthread_create (&t1, NULL, thread_main, &one);
+				int two = 2;
+				pthread_create (&t2, NULL, thread_main, &two);
 
 				pthread_join (t1, NULL);
 				pthread_join (t2, NULL);
--- a/configure	2023-06-14 17:18:48.000000000 +0200
+++ b/configure	2023-12-09 10:41:58.001084368 +0100
@@ -24906,14 +24894,16 @@
 			__thread int i;
 			static int res1, res2;
 
-			void thread_main (void *arg)
+			void *thread_main (void *parg)
 			{
+				int arg = *(int *)parg;
 				i = arg;
 				sleep (1);
 				if (arg == 1)
 					res1 = (i == arg);
 				else
 					res2 = (i == arg);
+				return NULL;
 			}
 
 			int main () {
@@ -24921,8 +24911,10 @@
 
 				i = 5;
 
-				pthread_create (&t1, NULL, thread_main, 1);
-				pthread_create (&t2, NULL, thread_main, 2);
+				int one = 1;
+				pthread_create (&t1, NULL, thread_main, &one);
+				int two = 2;
+				pthread_create (&t2, NULL, thread_main, &two);
 
 				pthread_join (t1, NULL);
 				pthread_join (t2, NULL);