[clang] [clang] Apply internal buffering to clang diagnostics printing (PR #113440)

[Timm Baeder via cfe-commits]

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@@ -133,12 +133,16 @@ void TextDiagnosticPrinter::HandleDiagnostic(DiagnosticsEngine::Level Level,
   // diagnostics in a context that lacks language options, a source manager, or
   // other infrastructure necessary when emitting more rich diagnostics.
   if (!Info.getLocation().isValid()) {
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tbaederr wrote:

So the problem you're describing only exists for diagnostics without valid locations? :thinking: 

https://github.com/llvm/llvm-project/pull/113440