Add env param to identify compilation with the coordinator

[ashtul]

It is required in order to enable using FT.PROFILE with a cursor on the coordinator but disable it on OSS.

[chayim]

-DRS_COORDINATOR is already passed down to the RediSearch build, from rscoordinator. Change your source to look for if(n)def RS_COORDINATOR. See the attached build log.

COORD.log

If you're curious - to generate this log, you can run make VERBOSE=1 as we're using CMake > 3.14 under the covers. I generated this by running: make VERBOSE=1|tee -ai COORD.log so that I could capture the outputs and see it in the console.

Validated on a fresh clone of master.