[lldb/test] Use SIGINT as the "stopping" signal

Using SIGSTOP means that if anything goes wrong in the test, the process
can end up in the stopped state, where it is not running, but still
taking up resources. Eventually, these "zombies" can make the machine
completely unusable. Instead, use a signal whose default action is to
kill the processes.

lldb/test/API/tools/lldb-server/main.cpp

@@ -355,7 +355,7 @@ int main(int argc, char **argv) {
       trap();
 #if !defined(_WIN32)
     } else if (arg == "stop") {
-      raise(SIGSTOP);
+      raise(SIGINT);
 #endif
     } else {
       // Treat the argument as text for stdout.