Fix non-portable use of /dev/null

/dev/null is not portable, so use File::Spec instead, which provides
portable "paths" and especially "nul" on Windows. I changed all places
with hard coded /dev/null to be sure, while I think it only is a
problem in direct system calls, because the other executed commands go
to sh.exe from MSYS which itself should port /dev/null to NUL. The
test still pass, so shouldn't have made any harm...

0 files changed, 0 insertions, 0 deletions