Fixed __kmpc_get_target_offload() to call initialization.

[AndreyChurbanov]

Summary

The __kmpc_get_target_offload() supposed to react on the OMP_TARGET_OFFLOAD environment variable setting.
Calling serial initialization causes the library to read the environment, then the routine returns correct value set by user.

[tlwilmar]

LGTM

openmp/trunk/runtime/src/kmp_csupport.cpp

void __kmpc_doacross_fini(ident_t *loc, int gtid) {
   // free private resources (need to keep buffer index forever)
   __kmp_thread_free(th, (void *)pr_buf->th_doacross_info);
   pr_buf->th_doacross_info = NULL;
   KA_TRACE(20, ("__kmpc_doacross_fini() exit: T#%d\n", gtid));
 }
 #endif
 
 #if OMP_50_ENABLED
-int __kmpc_get_target_offload(void) { return __kmp_target_offload; }
+int __kmpc_get_target_offload(void) {
+  if (!__kmp_init_serial) {
+    __kmp_serial_initialize();
+  }
+  return __kmp_target_offload;
+}
 #endif // OMP_50_ENABLED
 
 // end of file //