fix unused param "options" error in jemalloc_nodump_allocator.cc (#4738)

Summary:
Currently tests are failing on master with the following message:
> util/jemalloc_nodump_allocator.cc:132:8: error: unused parameter ‘options’ [-Werror=unused-parameter]
 Status NewJemallocNodumpAllocator(

This PR attempts to fix the issue
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4738

Differential Revision: D13278804

Pulled By: miasantreble

fbshipit-source-id: 64a6204aa685bd85d8b5080655cafef9980fac2f

util/jemalloc_nodump_allocator.cc

@@ -134,6 +134,7 @@ Status NewJemallocNodumpAllocator(
     std::shared_ptr<MemoryAllocator>* memory_allocator) {
   *memory_allocator = nullptr;
 #ifndef ROCKSDB_JEMALLOC_NODUMP_ALLOCATOR
+  (void) options;
   return Status::NotSupported(
       "JemallocNodumpAllocator only available with jemalloc version >= 5 "
       "and MADV_DONTDUMP is available.");