This decreases the link time, especially on desktop machines with many CPU
cores. However, it does come at a slight cost in binary size, making the flash
section about 200 bytes bigger for circuitplayground_express.
Before, linking build-circuitplayground_express/firmware.elf takes
8.8s elapsed time, leaving 3128 bytes free in flash.
After, linking build-circuitplayground_express/firmware.elf takes 2.8s elapsed
time, leaving 2924 bytes free in flash. (-6 seconds, -204 bytes free)
If necessary, we can make this per-board or even per-translation to squeeze full
builds.
396979a67e