Warn or fail early on dynamic builds with toolchain compiler and tcmalloc

It's tempting for MongoDB developers to use --link-model=dynamic to skip the slow link step when building the server. However, it's natural to also use tcmalloc (the default), the mongodbtoolchain compiler, and --dbg=on. This leads the server to crash with "memory allocation/deallocation mismatch", which is difficult to diagnose (SERVER-27675).

To save developers from a frustrating investigation, SCons should fail if it detects this combination of flags. Perhaps the rule is enforced within files like mongodbtoolchain_v3_gcc.vars and its family.