[OpenMP] Remove uses of ATOMIC_VAR_INIT

ATOMIC_VAR_INIT has a trivial definition
`#define ATOMIC_VAR_INIT(value) (value)`,
is deprecated in C17/C++20, and will be removed in newer standards in
newer GCC/Clang (e.g. https://reviews.llvm.org/D144196).

Author: MaskRay

openmp/runtime/src/kmp_global.cpp

@@ -63,8 +63,8 @@ int __kmp_init_counter = 0;
 int __kmp_root_counter = 0;
 int __kmp_version = 0;
 
-std::atomic<kmp_int32> __kmp_team_counter = ATOMIC_VAR_INIT(0);
-std::atomic<kmp_int32> __kmp_task_counter = ATOMIC_VAR_INIT(0);
+std::atomic<kmp_int32> __kmp_team_counter = 0;
+std::atomic<kmp_int32> __kmp_task_counter = 0;
 
 size_t __kmp_stksize = KMP_DEFAULT_STKSIZE;
 #if KMP_USE_MONITOR
@@ -386,7 +386,7 @@ int __kmp_debug_buf_atomic =
 
 char *__kmp_debug_buffer = NULL; /* Debug buffer itself */
 std::atomic<int> __kmp_debug_count =
-    ATOMIC_VAR_INIT(0); /* number of lines printed in buffer so far */
+    0; /* number of lines printed in buffer so far */
 int __kmp_debug_buf_warn_chars =
     0; /* Keep track of char increase recommended in warnings */
 /* end rotating debug buffer */
@@ -454,7 +454,7 @@ volatile kmp_info_t *__kmp_thread_pool = NULL;
 volatile kmp_team_t *__kmp_team_pool = NULL;
 
 KMP_ALIGN_CACHE
-std::atomic<int> __kmp_thread_pool_active_nth = ATOMIC_VAR_INIT(0);
+std::atomic<int> __kmp_thread_pool_active_nth = 0;
 
 /* -------------------------------------------------
  * GLOBAL/ROOT STATE */

openmp/runtime/src/kmp_lock.h

@@ -138,7 +138,7 @@ typedef union kmp_tas_lock kmp_tas_lock_t;
 //    kmp_tas_lock_t xlock = KMP_TAS_LOCK_INITIALIZER( xlock );
 #define KMP_TAS_LOCK_INITIALIZER(lock)                                         \
   {                                                                            \
-    { ATOMIC_VAR_INIT(KMP_LOCK_FREE(tas)), 0 }                                 \
+    { KMP_LOCK_FREE(tas), 0 }                                                  \
   }
 
 extern int __kmp_acquire_tas_lock(kmp_tas_lock_t *lck, kmp_int32 gtid);
@@ -276,11 +276,7 @@ typedef union kmp_ticket_lock kmp_ticket_lock_t;
 // Note the macro argument. It is important to make var properly initialized.
 #define KMP_TICKET_LOCK_INITIALIZER(lock)                                      \
   {                                                                            \
-    {                                                                          \
-      ATOMIC_VAR_INIT(true)                                                    \
-      , &(lock), NULL, ATOMIC_VAR_INIT(0U), ATOMIC_VAR_INIT(0U),               \
-          ATOMIC_VAR_INIT(0), ATOMIC_VAR_INIT(-1)                              \
-    }                                                                          \
+    { true, &(lock), NULL, 0U, 0U, 0, -1 }                                     \
   }
 
 extern int __kmp_acquire_ticket_lock(kmp_ticket_lock_t *lck, kmp_int32 gtid);

openmp/runtime/src/kmp_taskdeps.cpp

@@ -30,7 +30,7 @@
 // TODO: Any ITT support needed?
 
 #ifdef KMP_SUPPORT_GRAPH_OUTPUT
-static std::atomic<kmp_int32> kmp_node_id_seed = ATOMIC_VAR_INIT(0);
+static std::atomic<kmp_int32> kmp_node_id_seed = 0;
 #endif
 
 static void __kmp_init_node(kmp_depnode_t *node) {