Add coverage checking with gcov and lcov.
Add coverage checking with gcov and lcov.

ene-ilies/vi-firmware,openxc/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware