Revert "[CI] Disable LTC build from CI"

[antoniojkim]

Attempt to revert llvm/torch-mlir#3911 and run CI

[stellaraccident]

I believe that LTC needs its own testing bots. It shares practically no infra with the rest of the project, and while it is a fine thing to have in the repo if that is valuable to folks, the costs need to be paid by the people using it. One way to do that is by contributing a bot and test config tailored to what you need.