Turn checkbashisms into a make target

make_gitrev.sh actually breaks checkbashisms' parser,
which /insists/ that the end-of-line " is actually a string start

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12101