Add a --crash option to not.

Now the two possible uses of not are
* not cmd
  Will return true if cmd doesn't crash and returns false.
* not --crash cmd
  Will return true if cmd crashes.

It will be used/tested in a followup commit for the clang crash recovery
testing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185678 91177308-0d34-0410-b5e6-96231b3b80d8

utils/not/not.cpp

@@ -13,14 +13,33 @@
 using namespace llvm;
 
 int main(int argc, const char **argv) {
-  std::string Program = sys::FindProgramByName(argv[1]);
+  bool ExpectCrash = false;
+
+  ++argv;
+  --argc;
+
+  if (argc > 0 && StringRef(argv[0]) == "--crash") {
+    ++argv;
+    --argc;
+    ExpectCrash = true;
+  }
+
+  if (argc == 0)
+    return 1;
+
+  std::string Program = sys::FindProgramByName(argv[0]);
 
   std::string ErrMsg;
-  int Result = sys::ExecuteAndWait(Program, argv + 1, 0, 0, 0, 0, &ErrMsg);
+  int Result = sys::ExecuteAndWait(Program, argv, 0, 0, 0, 0, &ErrMsg);
   if (Result < 0) {
     errs() << "Error: " << ErrMsg << "\n";
+    if (ExpectCrash)
+      return 0;
     return 1;
   }
 
+  if (ExpectCrash)
+    return 1;
+
   return Result == 0;
 }