[Support/Timer] Make GetMallocUsage() aware of jemalloc.

Differential Revision:	D7657
Reviewed by:	shankarke, majnemer


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229824 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed