Add an explicit initialization to work around what appears to be a valgrind
false positive, at least on Darwin. I haven't filed this, but you can feel free.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115242 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Unix/Program.inc b/lib/System/Unix/Program.inc
index 0209f5a..bbb029c 100644
--- a/lib/System/Unix/Program.inc
+++ b/lib/System/Unix/Program.inc
@@ -212,7 +212,9 @@
       envp = const_cast<const char **>(*_NSGetEnviron());
 #endif
 
-    pid_t PID;
+    // Explicitly initialized to prevent what appears to be a valgrind false
+    // positive.
+    pid_t PID = 0;
     int Err = posix_spawn(&PID, path.c_str(), &FileActions, /*attrp*/0,
                           const_cast<char **>(args), const_cast<char **>(envp));