[llvm] [flang-rt] Optimise ShallowCopy and use it in CopyInAssign (PR #140569)

[Kajetan Puchalski via llvm-commits]

mrkajetanp wrote:

> Always make sure that the pre commit ci pass before merging.

It did, the issue was that I did not freshly rebase the PR before merging and the variable changed after the last rebase.

https://github.com/llvm/llvm-project/pull/140569