[TargetLibraryInfo] fix finite mathlib function availability

This patch was part of:
https://reviews.llvm.org/D41338
...but we can expose the bug in IR via constant propagation
as shown in the test. Unless the triple includes 'linux', we
should not fold these because the functions don't exist on
other platforms (yet?).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322010 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed