[llvm] [NFC][Support] Create helper function to parse bool. (PR #102818)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Note, linux build failues look like infra issues: 

  | fatal: not a git repository (or any parent up to mount point /var/lib)

I don't have permission to rekick. Hoping it gets kicked when I update the branch again (and the infa issue resolve by that time)

https://github.com/llvm/llvm-project/pull/102818