Fix memory leaks in clang-offload-bundler

Summary:
1. Pair removed from StringMap was not destroyed
2. ObjectFile had no owner

Reviewers: sfantao

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23865

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@279722 91177308-0d34-0410-b5e6-96231b3b80d8