Replace 'which' with 'command -v' to test for the existance of an executable
This is considered to be more robust.
Two instances remain:
scripts/build/chroot_archives, line 257: if [ "${LB_APT}" = "aptitude" ] && [ ! $(Chroot chroot "which aptitude") ] The command is run inside a chroot where the environment might be special, and would need further testing.
manpages/Makefile, line 42:
@if [ ! -x "$$(which po4a 2>/dev/null)" ];
I am insufficiently familiar with makefile syntax to edit this.