[llvm] Reapply: [lit] Avoid multiprocessing for -j1 runs (PR #179824)

[Henrik G. Olsson via llvm-commits]

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@@ -162,7 +162,13 @@ def startTimer(self):
 
     def _handleTimeoutReached(self):
         self._timeoutReached = True
-        self._kill()
+        try:
+            self._kill()
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hnrklssn wrote:

Do we still need this after catching additional errors in `killProcessAndChildren()`? I'm a bit suspicious that the broad catch without any diagnostics could end up hiding other bugs.

https://github.com/llvm/llvm-project/pull/179824