[lld] [LLD][COFF] Set the Thumb bit on locally imported ARMNT function poin… (PR #215919)

[Martin Storsjö via llvm-commits]

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

LGTM. I've reproduced the issue locally, and can confirm that this PR fixes it. The fix looks reasonable.

The testcase could possibly be written differently, but this can be acceptable as well.

https://github.com/llvm/llvm-project/pull/215919