[libc][stdlib] Remove LIBC_THREAD_LOCAL from rand_next

srand and rand do not need to be threadsafe, so it should be permissible
to remove thise from rand_next whose only users are srand and rand. This
is helpful for the baremetal runtimes where we still need to setup the
TLS machinery.

Author: PiJoules

libc/src/stdlib/rand_util.cpp

@@ -18,7 +18,7 @@ ThreadLocal<unsigned long> rand_next;
 #else
 // C standard 7.10p2: If 'rand' is called before 'srand' it is to proceed as if
 // the 'srand' function was called with a value of '1'.
-LIBC_THREAD_LOCAL unsigned long rand_next = 1;
+unsigned long rand_next = 1;
 #endif
 
 } // namespace LIBC_NAMESPACE

libc/src/stdlib/rand_util.h

@@ -34,7 +34,7 @@ template <typename T> class ThreadLocal {
 
 extern ThreadLocal<unsigned long> rand_next;
 #else
-extern LIBC_THREAD_LOCAL unsigned long rand_next;
+extern unsigned long rand_next;
 #endif
 
 } // namespace LIBC_NAMESPACE