[llvm] [CAS] Add MappedFileRegionArena (PR #114099)

[Steven Wu via llvm-commits]

cachemeifyoucan wrote:

> This patch breaks both the [Solaris/sparcv9](https://lab.llvm.org/buildbot/#/builders/13/builds/9575) and [Solaris/amd64](https://lab.llvm.org/staging/#/builders/120/builds/12336) buildbots.

I will disable solaris as well. I need to read some documentation about that. It seems the OS is running out of lock resources? I don't think too much locks are used so I will workaround while I investigate.

https://github.com/llvm/llvm-project/pull/114099