Fix a compilation error.
Fix a compilation error.

Fix a compilation error that occurs if Valgrind is not enabled.  This
regression was caused by b2c0d6322d2307458ae2b28545f8a5c9903d7ef5 (Add
witness, a simple online locking validator.).

8l/jemalloc,glandium/jemalloc,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,AndroidExternal/jemalloc,wqfish/jemalloc,glandium/jemalloc,glandium/jemalloc,leebaok/jemalloc-4.2.1-readcode,8l/jemalloc,wqfish/jemalloc,jemalloc/jemalloc-cmake,8l/jemalloc,glandium/jemalloc,AndroidExternal/jemalloc,leebaok/jemalloc-4.2.1-readcode,wqfish/jemalloc,leebaok/jemalloc-4.2.1-readcode,leebaok/jemalloc-4.2.1-readcode,AndroidExternal/jemalloc,wqfish/jemalloc,wqfish/jemalloc,8l/jemalloc,jemalloc/jemalloc-cmake,AndroidExternal/jemalloc