[libc++] Make atomic contention tables constinit (#207456)

libcxx/src/atomic.cpp

diff --git a/libcxx/src/atomic.cpp b/libcxx/src/atomic.cpp
index ae79ac7..53aec09 100644
--- a/libcxx/src/atomic.cpp
+++ b/libcxx/src/atomic.cpp
@@ -422,7 +422,7 @@
   constexpr __contention_state_native() : __waiter_count(0) {}
 };
 
-static __contention_state_native __contention_table_native[__contention_table_size];
+static constinit __contention_state_native __contention_table_native[__contention_table_size];
 
 static __cxx_atomic_contention_t* __get_native_waiter_count(void const* p) {
   return &__contention_table_native[__contention_hasher(p) & (__contention_table_size - 1)].__waiter_count;
@@ -438,7 +438,7 @@
   constexpr __contention_state_global() : __waiter_count(0), __platform_state(0) {}
 };
 
-static __contention_state_global __contention_table_global[__contention_table_size];
+static constinit __contention_state_global __contention_table_global[__contention_table_size];
 
 static __contention_state_global* __get_global_contention_state(void const* p) {
   return &__contention_table_global[__contention_hasher(p) & (__contention_table_size - 1)];