Dealing with an outdoor grill with a bad gas line
Converting to propane is probably the only viable option. I don't know what the code is in your area but the gas line being in contact with the concrete suggests that it's not to code. Gas lines underground should be in a chase and buried to a set depth. It should never touch the concrete. My code states a minimum of 18" depth, it can't exit the building underground through the foundation and it must be flexible. Plastic gas line is approved for direct burial but uses pre sleeved risers to penetrate the ground. Your gas line is leaking so it should be rendered inoperable by disconnecting it at the valve and capping it. A propane conversion is relatively easy to do. If you can't find the appropriate kit, universal burner kits are available. 

I'm not sure if this applies to you. It's aTurbo conversion PDF. If you reference the model number it would be helpful. It's on there somewhere. Sometimes the built in barbecues have information on a tag attached by the regulator. 

Another potential option is to repair the pipe. Assuming that the line is "to code" up to the break, the line could be repaired by breaking the concrete around it and continuing the chase higher after a joint in the pipe is made. This would only apply if the "floor" was poured above the original "to code" gas line install and caused the damage.