As part of our plan for monitoring and investigating the sporadic heap corruptions in SpiderMonkey (https://jira.mongodb.org/browse/SERVER-89758 ) , we would like to perform more rigorous garbage collection stress testing. 

https://jira.mongodb.org/browse/SERVER-91111 enables a new build variant on evergreen which toggles the spider-monkey-dbg mode, and further, allows us to specify JS_GC_ZEAL settings as an environment variable to resmoke.py. 

Unfortunately, using the environment variable method for resmoke means that both the mongo (shell) and mongod process inherit the JS_GC_ZEAL setting, and makes the test runtime too long (over 5 hours) with more rigorous zeal settings.

As part of this ticket, provide a way to provide the JS_GC_ZEAL parameter setting only to mongod when running the evergreen build variant. The hope is that by doing this, we we will be able to run a wider variety of the GC zeal settings without timing out on the CI infrastructure.