rpm: Fix make rpm on Debian/Ubuntu

The recent patch to change the bash completion install location based
on the Distribution, ignored that it should still be possible to
create RPMs on Debian derived systems. Additionally `make deb` itself
creates RPMs and converts them via `alien`.

This patch adds the bashcompletiondir variable to the rpm defines and
uses this for the location, where to get the bash completion file.

It still changes the location on Debian/Ubuntu systems in the final
packages from /etc/bash_completion.d to
/usr/share/bash-completion/completions

Fixes: e69ade3

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Closes openzfs#15355
Closes openzfs#15365

config/zfs-build.m4

@@ -358,6 +358,9 @@ AC_DEFUN([ZFS_AC_RPM], [
 	AS_IF([test -n "$udevruledir" ], [
 		RPM_DEFINE_UTIL=${RPM_DEFINE_UTIL}' --define "_udevruledir $(udevruledir)"'
 	])
+	AS_IF([test -n "$bashcompletiondir" ], [
+		RPM_DEFINE_UTIL=${RPM_DEFINE_UTIL}' --define "_bashcompletiondir $(bashcompletiondir)"'
+	])
 	RPM_DEFINE_UTIL=${RPM_DEFINE_UTIL}' $(DEFINE_SYSTEMD)'
 	RPM_DEFINE_UTIL=${RPM_DEFINE_UTIL}' $(DEFINE_PYZFS)'
 	RPM_DEFINE_UTIL=${RPM_DEFINE_UTIL}' $(DEFINE_PAM)'

rpm/generic/zfs.spec.in

@@ -522,7 +522,7 @@ systemctl --system daemon-reload >/dev/null || true
 %config(noreplace) %{_sysconfdir}/%{name}/vdev_id.conf.*.example
 %attr(440, root, root) %config(noreplace) %{_sysconfdir}/sudoers.d/*
 
-%config(noreplace) %{_sysconfdir}/bash_completion.d/zfs
+%config(noreplace) %{_bashcompletiondir}/zfs
 
 %files -n libzpool5
 %{_libdir}/libzpool.so.*