Fix memory leak in usingJEMalloc()

Summary: We should probably just free this.

Reviewed By: yfeldblum

Differential Revision: D20119718

fbshipit-source-id: 2a6c79730243b7af5ba90dac631ce0c8e1e0e6a4

folly/memory/Malloc.h

@@ -116,12 +116,14 @@ FOLLY_NOINLINE inline bool usingJEMalloc() noexcept {
 
     uint64_t origAllocated = *counter;
 
-    static const void* volatile ptr = malloc(1);
+    static void* volatile ptr = malloc(1);
     if (!ptr) {
       // wtf, failing to allocate 1 byte
       return false;
     }
 
+    free(ptr);
+
     return (origAllocated != *counter);
   }
   ();