[openmp] [test] Fix warnings about printf format mismatches on Windows

[mstorsjo]

Summary

This fixes warnings like this:

openmp/runtime/test/omp_testsuite.h:107:60: warning: format specifies type 'unsigned int' but the argument has type 'DWORD' (aka 'unsigned long') [-Wformat]
    fprintf(stderr, "CreateThread() failed: Error #%u.\n", GetLastError());
                                                   ~~      ^~~~~~~~~~~~~~
                                                   %lu

[Meinersbur]

LGTM

openmp/runtime/test/omp_testsuite.h

static int pthread_create(pthread_t *thread, void *attr,
                           void *(*start_routine) (void *), void *arg) {
   pthread_t pthread;
   struct thread_func_info_t* info;
   info = (struct thread_func_info_t*)malloc(sizeof(struct thread_func_info_t));
   info->start_routine = start_routine;
   info->arg = arg;
   pthread = CreateThread(NULL, 0, __thread_func_wrapper, info, 0, NULL);
   if (pthread == NULL) {
-    fprintf(stderr, "CreateThread() failed: Error #%u.\n", GetLastError());
+    fprintf(stderr, "CreateThread() failed: Error #%u.\n",
+            (unsigned) GetLastError());
     exit(1);
   }
   *thread = pthread;
   return 0;
 }
 // retval is ignored for now
 static int pthread_join(pthread_t thread, void **retval) {
   int rc;
   rc = WaitForSingleObject(thread, INFINITE);
   if (rc == WAIT_FAILED) {
     fprintf(stderr, "WaitForSingleObject() failed: Error #%u.\n",
-            GetLastError());
+            (unsigned) GetLastError());
     exit(1);
   }
   rc = CloseHandle(thread);
   if (rc == 0) {
-    fprintf(stderr, "CloseHandle() failed: Error #%u.\n", GetLastError());
+    fprintf(stderr, "CloseHandle() failed: Error #%u.\n",
+            (unsigned) GetLastError());
     exit(1);
   }
   return 0;
 }
 #else
 # include <pthread.h>
 #endif
 
 #endif