[clang] [llvm] remove redundant uses of `isa` caught by clang-tidy (NFC) (PR #192813)

[Henrik G. Olsson via cfe-commits]

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@@ -66,7 +66,7 @@ GetCC1Arguments(DiagnosticsEngine *Diagnostics,
   // We expect to get back exactly one Command job, if we didn't something
   // failed. Extract that job from the Compilation.
   const driver::JobList &Jobs = Compilation->getJobs();
-  if (!Jobs.size() || !isa<driver::Command>(*Jobs.begin()))
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hnrklssn wrote:

I didn't include the `cast` fixes in this PR because there are so many more of them, I haven't had time to go through them all yet. But clang-tidy did indeed remove the cast as well, and it makes sense to remove them both at once since they are related.

https://github.com/llvm/llvm-project/pull/192813