[clang] [llvm] [clang] Support multiple in-process cc1 jobs in a ToolSession (PR #222531)

[Alexandre Ganea via cfe-commits]

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aganea wrote:

I think you should move this below even if the target time-trace file cannot be sucessfully open. Otherwise if a file open failure happens on the first job, the second job would assert.

https://github.com/llvm/llvm-project/pull/222531