Attaching a debugger to a process takes several seconds. This is longer then the time it takes to run some tests.

To add the ability to debug resmoke tests, it is helpful for mongo daemons to wait for the debugger to attach before continuing. For most tests, when they wait is opted into, the extra startup delay should impose no issues because resmoke.py/servers.js already wait for process startup today.

In the first version, this check can be done with an environment variable when a flag is specified to SConstruct. An environment variable has a benefit in that it can be checked before global initializers are called.