[llvm] [MachineVerifier] Report errors from one thread at a time (PR #111605)

[Matt Arsenault via llvm-commits]

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@@ -93,21 +95,29 @@ using namespace llvm;
 
 namespace {
 
+static ManagedStatic<sys::SmartMutex<true>> ReportedErrorsLock;
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arsenm wrote:

Document this 

https://github.com/llvm/llvm-project/pull/111605