[llvm] [ADT] Add a missing call to a unique_function destructor after move (PR #98747)

[Dmitry Yanovsky via llvm-commits]

kerambyte wrote:

Added a simple unit-test that counts the number of times the destructor is called. Checked locally that without my fix we get 3 calls and with it we get 4.

https://github.com/llvm/llvm-project/pull/98747