[AIX][lit] Don't depend on psutil on AIX

Summary:
On AIX psutil can run into problems with permissions to read the process
tree, which causes problems for python timeout tests which need to kill off
a test and it's children.

This patch adds a workaround by invoking shell via subprocess and using a
platform specific option to ps to list all the descendant processes so we can
kill them. We add some checks so lit can tell whether timeout tests are
supported with out exposing whether we are utilizing the psutil
implementation or the alternative.

Reviewers: hubert.reinterpretcast, andusy, davide, delcypher

Reviewed By: delcypher

Subscribers: davide, delcypher, christof, lldb-commits, libcxx-commits, llvm-commits

Tags: #lldb, #libc, #llvm

Differential Revision: https://reviews.llvm.org/D64251

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@366912 91177308-0d34-0410-b5e6-96231b3b80d8

utils/libcxx/util.py

@@ -253,24 +253,27 @@ def killProcessAndChildren(pid):
     TODO: Reimplement this without using psutil so we can
           remove our dependency on it.
     """
-    import psutil
-    try:
-        psutilProc = psutil.Process(pid)
-        # Handle the different psutil API versions
+    if platform.system() == 'AIX':
+        subprocess.call('kill -kill $(ps -o pid= -L{})'.format(pid), shell=True)
+    else:
+        import psutil
         try:
-            # psutil >= 2.x
-            children_iterator = psutilProc.children(recursive=True)
-        except AttributeError:
-            # psutil 1.x
-            children_iterator = psutilProc.get_children(recursive=True)
-        for child in children_iterator:
+            psutilProc = psutil.Process(pid)
+            # Handle the different psutil API versions
             try:
-                child.kill()
-            except psutil.NoSuchProcess:
-                pass
-        psutilProc.kill()
-    except psutil.NoSuchProcess:
-        pass
+                # psutil >= 2.x
+                children_iterator = psutilProc.children(recursive=True)
+            except AttributeError:
+                # psutil 1.x
+                children_iterator = psutilProc.get_children(recursive=True)
+            for child in children_iterator:
+                try:
+                    child.kill()
+                except psutil.NoSuchProcess:
+                    pass
+            psutilProc.kill()
+        except psutil.NoSuchProcess:
+            pass
 
 
 def executeCommandVerbose(cmd, *args, **kwargs):