[SjLjEHPrepare] Don't grab pointers to functions in doInitialization

Certain optimization passes (like globaldce) can prune function
declaration that SjLjEHPrepare assumed would exit when it'd
runOnFunction.

This fixes PR26669.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@261303 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed