[llvm-symbolizer] Add -exe, -e as aliases to -obj

Summary: Provides -exe, -e as aliases to -obj. Motivation: https://bugs.llvm.org/show_bug.cgi?id=40071

Reviewers: ruiu, rnk, fjricci, jhenderson

Reviewed By: jhenderson

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D56580

llvm-svn: 350925