[NFC] Fix `-Wcast-qual` warnings in Darwin `internal_sysctl(...)` implementation.

[delcypher]

Summary

The warnings were introduced in r341187 and r341192.

[delcypher]

@krytarowski Thanks for the quick review. I'll wait for @kubamracek or @george.karpenkov to also review before landing.

compiler-rt/trunk/lib/sanitizer_common/sanitizer_mac.cc

 int internal_fork() {
   if (&__fork)
     return __fork();
   return fork();
 }
 
 int internal_sysctl(const int *name, unsigned int namelen, void *oldp,
                     uptr *oldlenp, const void *newp, uptr newlen) {
-  return sysctl((int *)name, namelen, oldp, (size_t *)oldlenp, (void *)newp,
-                (size_t)newlen);
+  return sysctl(const_cast<int *>(name), namelen, oldp, (size_t *)oldlenp,
+                const_cast<void *>(newp), (size_t)newlen);
 }
 
 int internal_forkpty(int *amaster) {
   int master, slave;
   if (openpty(&master, &slave, nullptr, nullptr, nullptr) == -1) return -1;
   int pid = internal_fork();
   if (pid == -1) {
     close(master);