Without this, hardware that requires firmware (e.g. Saleae Logic) is
unuseable.
Example error that this fixes:
sr: ezusb: Unable to open firmware file /nix/store/rqgppsz3gwy8jailflf3049fzyzrgkdb-libsigrok-0.3.0/share/sigrok-firmware/fx2lafw-saleae-logic.fw for reading: No such file or directory
sr: fx2lafw: Firmware upload failed for device 0.