[llvm] TargetLibraryInfo: Assume no libcalls in the default constructor (PR #92400)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Seems reasonable to me, though someone who knows more of the details in this area may want to chime in. Hopefully we can clean up some of this logic in the future. 

https://github.com/llvm/llvm-project/pull/92400