Delete the buffer in createObjectFile if it fails.

The Binary constructor takes ownership of the memory buffer. This is a fairly
unfortunate interface, but for now make createObjectFile consistent with it
by also deleting the buffer if it fails.

Fixes a leak in llvm-ar found by the valgrind bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187039 91177308-0d34-0410-b5e6-96231b3b80d8