[clang] [clang] Allow custom bug report messages (PR #157536)

[Alan Zhao via cfe-commits]

alanzhao1 wrote:

I spoke with @rnk offline and he suggested that based on the previous two comments we should track this discussion in a bug, so I created https://github.com/llvm/llvm-project/issues/158203.

In the meantime I'll close this PR to put it on hold.

https://github.com/llvm/llvm-project/pull/157536