Fix: Add missing mkdir command in Makefile

[dzatoah]

Hey,

This PR fixes a missing mkdir command in Makefile.

By the way:
We are currently working on packaging openNDS for Debian.
See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1009368

For the Debian package we will use $(DESTDIR)/lib/systemd/system/ instead of $(DESTDIR)/etc/systemd/system.
Do you wish that I include this change in this PR too?

[bluewavenet]

@dzatoah
I think the missing mkdir is only an issue for Debian and Debian based, because it does not already exist there. I don't see adding it in anyway being a problem though.

For the Debian package we will use $(DESTDIR)/lib/systemd/system/ instead of $(DESTDIR)/etc/systemd/system.

This should not be incorporated into the generic Makefile as it will break other distros. Specific requirements of a distro should be included in a specific area for the distro. This is already done for both Debian and OpenWrt (see linux_debian and linux_openwrt folders).

[sunweaver]

@bluewavenet For creating packages (independent from the distribution), the upstream Makefile (or whatever build system is used by upstream) must assure that the complete directory structure required for putting upstream files in gets created by that Makefile.

With RPM and Debian packaging, the make install target gets created on an empty DESTDIR and the upstream Makefile is then responsible for creating everything in DESTDIR.

This is definitely not a Debian-specific issue. You cannot assume in Makefile's install target for any directories being already present.

(says sunweaver, [1])

[1] https://qa.debian.org/developer.php?email=sunweaver%40debian.org