build-aux/pkg-version should use /bin/bash instead of /bin/sh in his shebang or the bashishm should be fixed:

possible bashism in build-aux/pkg-version line 26 (should be 'b = a'):
    if [ "x${version}" == "x" ] ; then
possible bashism in build-aux/pkg-version line 49 (should be 'b = a'):
    if [ "x${release}" == "x" ] ; then