Allow the user to specify the compiler via environment variable

[hmcfgusb] / hmcfgusb.rules

SUBSYSTEMS=="usb" ATTRS{idVendor}=="1b1f" ATTRS{idProduct}=="c00f" MODE:="0666"
SUBSYSTEMS=="usb" ATTRS{idVendor}=="1b1f" ATTRS{idProduct}=="c010" MODE:="0666"