Fix the clean rule
It now blows away $ARCH/bin without thinking hard (because, stupidly, amd64/bin includes
some rc scripts, i.e. not binaries -- wtf?) and all the .a's in lib. Then, to undo
any possible damage, it does a checkout of $ARCH/bin
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>