[scudo] Add mallopt to print stats to the log.

compiler-rt/lib/scudo/standalone/include/scudo/interface.h

 #define M_MEMTAG_TUNING_BUFFER_OVERFLOW 0
 #endif
 
 // Tune for use-after-free.
 #ifndef M_MEMTAG_TUNING_UAF
 #define M_MEMTAG_TUNING_UAF 1
 #endif
 
+// Print internal stats to the log.
+#ifndef M_LOG_STATS
+#define M_LOG_STATS -205
+#endif
+
 } // extern "C"
 
 #endif // SCUDO_INTERFACE_H_

compiler-rt/lib/scudo/standalone/wrappers_c.inc

SCUDO_ALLOCATOR.setOption(scudo::Option::ReleaseInterval,
                               static_cast<scudo::sptr>(value));
     return 1;
   } else if (param == M_PURGE) {
     SCUDO_ALLOCATOR.releaseToOS(scudo::ReleaseToOS::Force);
     return 1;
   } else if (param == M_PURGE_ALL) {
     SCUDO_ALLOCATOR.releaseToOS(scudo::ReleaseToOS::ForceAll);
     return 1;
+  } else if (param == M_LOG_STATS) {
+    SCUDO_ALLOCATOR.printStats();
+    return 1;
   } else {
     scudo::Option option;
     switch (param) {
     case M_MEMTAG_TUNING:
       option = scudo::Option::MemtagTuning;
       break;
     case M_THREAD_DISABLE_MEM_INIT:
       option = scudo::Option::ThreadDisableMemInit;