The source project of this merge request has been removed.
configure.ac: fix bashisms
In commit 9bcc97bc a new feature was added, which used bash-specific features in a POSIX sh script. This caused configure to completely fail with syntax errors on systems where /bin/sh was not symlinked to GNU bash.
== is a bash-specific alias for = and should never, ever, ever be
used since it offers no additional utility for bash but merely serves
to confuse people writing POSIX.
substring parameter expansion, e.g. ${with_tmpfilesdir:0:1} is not
POSIX but can be trivially replaced by case wildcards.