[llvm] [docs] Release man pages (PR #201376)

[Konrad Kleine via llvm-commits]

kwk wrote:

> Is there a reason this needs to be separate workflow, can we just add the man pages to the existing documentation build?

Adding the man page steps to the existing documentation workflow required some adjustments that can be found in [04d3730](https://github.com/llvm/llvm-project/pull/201376/commits/04d37302c9b6e0d309b48a19340c1f4e2d85cd53).

https://github.com/llvm/llvm-project/pull/201376