[esan|wset] Add working set tool driver flags

Summary:
Adds a new -fsanitize=efficiency-working-set flag to enable esan's working
set tool.  Adds appropriate tests for the new flag.

Reviewers: aizatsky

Subscribers: vitalybuka, zhaoqin, kcc, eugenis, llvm-commits

Differential Revision: http://reviews.llvm.org/D20484

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@270641 91177308-0d34-0410-b5e6-96231b3b80d8