[clang] [clang][Diagnostics] Only record lexer check points when colors are enabled (PR #204926)

[Alexis Engelke via cfe-commits]

aengelke wrote:

> also, any idea how I could make a comparison in the tracker before actually merging?

See [here](https://llvm-compile-time-tracker.com/about.php).

https://github.com/llvm/llvm-project/pull/204926