[clang] [CIR][OpenMP] Implement lowering for the 'num_threads' clause for 'parallel' directive (PR #202466)

[Pedro da Rosa Pinheiro via cfe-commits]

pedropiin wrote:

@andykaylor I've fixed the PR according to your comments on my other PR #204999 . Could you please take a whenever you get some time? 

https://github.com/llvm/llvm-project/pull/202466