As far as I can tell, Luminary microcontrollers are Cortex-M3 based, and should be fully supported by recent GCC versions.
You can obtain an installable package of GCC configured as an ARM cross-compiler from CodeSourcery web site (or you can build one from sources yourself).
I work with LM3S6965 a cortex-M3, and arm-none-eabi-gcc version 4.3.2, this is the gcc from Codesourcey, openocd to write flash and to debug,jtag from olimex, and freeRtos as my RTOS.