build: don't hardcode the compiler (gmcs) for the 'hg' target
build: don't hardcode the compiler (gmcs) for the 'hg' target

Let's use the $(MCS) env var, set up by the configure phase.

GNOME/banshee,dufoli/banshee,GNOME/banshee,GNOME/banshee,Carbenium/banshee,babycaseny/banshee,GNOME/banshee,arfbtwn/banshee,ixfalia/banshee,dufoli/banshee,ixfalia/banshee,arfbtwn/banshee,stsundermann/banshee,stsundermann/banshee,babycaseny/banshee,dufoli/banshee,Carbenium/banshee,stsundermann/banshee,stsundermann/banshee,ixfalia/banshee,GNOME/banshee,GNOME/banshee,dufoli/banshee,babycaseny/banshee,dufoli/banshee,ixfalia/banshee,ixfalia/banshee,stsundermann/banshee,babycaseny/banshee,arfbtwn/banshee,babycaseny/banshee,GNOME/banshee,babycaseny/banshee,ixfalia/banshee,Carbenium/banshee,stsundermann/banshee,dufoli/banshee,stsundermann/banshee,arfbtwn/banshee,dufoli/banshee,Carbenium/banshee,arfbtwn/banshee,arfbtwn/banshee,ixfalia/banshee,dufoli/banshee,Carbenium/banshee,arfbtwn/banshee,GNOME/banshee,stsundermann/banshee,arfbtwn/banshee,Carbenium/banshee,ixfalia/banshee,babycaseny/banshee,babycaseny/banshee