[clang] [clang] Implement -fstrict-bool (PR #116732)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

I second that we need to document how values outside of zero and one are handled. 

I would like also really want to see a test that demonstrates the behavior we are expecting to support with comments explaining the result and why we expect it. 

After seeing an example of the behavior you expect we can have a wider discussion whether we really want to support that or not.

https://github.com/llvm/llvm-project/pull/116732