[OpenMP][Fix] Conditional compilation leaves variables unused

[gtbercea]

Summary

Prevent variables from being left unused by conditional compilation.

[Hahnfeld]

The call must not be put into conditional compilation. As discussed in D50774 there are two options:

1. Guard the variable definition and assignment (the first line) by preprocessor guards.
2. Add a (void) *_status; to silence the warning.

I think the latter one is used many times in Clang, so I'd favor that.

[gtbercea]

Add implicit cast.

[Hahnfeld]

LG

runtime/src/kmp_csupport.cpp

if (ompt_enabled.ompt_callback_mutex_acquire) {
           ompt_mutex_nest_lock, omp_lock_hint_none,
           __ompt_get_mutex_impl_type(user_lock), (omp_wait_id_t)user_lock,
           codeptr);
     }
   }
 #endif
   int acquire_status =
       KMP_D_LOCK_FUNC(user_lock, set)((kmp_dyna_lock_t *)user_lock, gtid);
+  (void) acquire_status;
 #if USE_ITT_BUILD
   __kmp_itt_lock_acquired((kmp_user_lock_p)user_lock);
 #endif
 
 #if OMPT_SUPPORT && OMPT_OPTIONAL
   if (ompt_enabled.enabled) {
     if (acquire_status == KMP_LOCK_ACQUIRED_FIRST) {
       if (ompt_enabled.ompt_callback_mutex_acquired) {

 void __kmpc_unset_nest_lock(ident_t *loc, kmp_int32 gtid, void **user_lock) {
 #if KMP_USE_DYNAMIC_LOCK
 
 #if USE_ITT_BUILD
   __kmp_itt_lock_releasing((kmp_user_lock_p)user_lock);
 #endif
   int release_status =
       KMP_D_LOCK_FUNC(user_lock, unset)((kmp_dyna_lock_t *)user_lock, gtid);
+  (void) release_status;
 
 #if OMPT_SUPPORT && OMPT_OPTIONAL
   // This is the case, if called from omp_init_lock_with_hint:
   void *codeptr = OMPT_LOAD_RETURN_ADDRESS(gtid);
   if (!codeptr)
     codeptr = OMPT_GET_RETURN_ADDRESS(0);
   if (ompt_enabled.enabled) {
     if (release_status == KMP_LOCK_RELEASED) {