[esan] Add support for log_exe_name

Summary:
Adds the call needed to cache the binary name to support the sanitizer
option log_exe_name for usable log file results when running multiple
applications.  Adds a test.

Reviewers: aizatsky

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

Differential Revision: http://reviews.llvm.org/D20747

llvm-svn: 271586