[flang] [llvm] [flang][OpenMP] Inline the firstprivate array copy instead of calling Assign() (PR #211543)

[Sairudra More via llvm-commits]

https://github.com/Saieiei requested changes to this pull request.

Thanks for working on this. I left two comments below.

https://github.com/llvm/llvm-project/pull/211543