Add regression test for pthread argument escape in region analysis

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Co-authored-by: michael-schwarz <13812333+michael-schwarz@users.noreply.github.com>

Author: Copilot

tests/regression/09-regions/41-escape_rc_norace.c

@@ -0,0 +1,28 @@
+// PARAM: --set ana.activated[+] "'region'"
+// Regression: pthread argument properly tracked as escaped in region analysis.
+// The region analysis must treat a local variable passed via pthread argument
+// as escaped (global), enabling proper race detection.
+// The NORACE variant (same mutex) shows no false positives.
+// See also 09/34 which is the RACE variant with different mutexes.
+#include <pthread.h>
+
+pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+
+void *t_fun(void *arg) {
+  int *p = (int *) arg;
+  pthread_mutex_lock(&mutex);
+  (*p)++; // NORACE
+  pthread_mutex_unlock(&mutex);
+  return NULL;
+}
+
+int main(void) {
+  pthread_t id;
+  int i;
+  pthread_create(&id, NULL, t_fun, (void *) &i);
+  pthread_mutex_lock(&mutex);
+  i++; // NORACE
+  pthread_mutex_unlock(&mutex);
+  pthread_join(id, NULL);
+  return 0;
+}