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

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AnonMiraj wrote:



> This seems to be actually a regression, at least in some cases: https://llvm-compile-time-tracker.com/compare.php?from=aab2ff0b9096df1d5168e293c81b6653e759890d&to=592953beff733a1e28f6c6e5e39f948fb035a329&stat=instructions:u

yeah, it looks like I misunderstood the change that happened mid-PR in 2a215f473fb9 to how `getShowColors()` works. here is the fix #209355.

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

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