Right now the top level SConstruct is cluttered with configure test definitions that have complex test bodies. The configure tests are injected into local Configure objects as needed.

This both clutters the SConstruct with lots of test bodies and code to inject the configure tests, but makes it hard to re-execute a configure check. As a result, we locally cache configure test results in free variables.

The whole thing becomes hard to follow. We should migrate the configure check bodies and injection into the Configure context into a new mongoconfig tool in site_scons/site_tools.