new easyblock for systemd_wrapper

[Micket]

(created using eb --new-pr)

My motivation for this is

1. add pkgconfig files into a path that EB can see, since EB can't find the /usr/share/pkgconfig/*.pc files as to not pick up OS things unintionally
2. One idea i had for extending this was to add the devel-part of this package as optional source, so you'd use the libsystemd.so and libudev.so from the OS, but add the headers in EB. I didn't do this yet as there is quite a bit more work for that.

[Micket]

Hrm.. i guess i need to deal with errors of not finding things outside of the init method.

Also, I'm not sure why, but I can't get the sanity check step to ever fail. It always passes no matter if it finds those paths or not.

[Micket]

So, I'm not sure how useful this thing is. At this point, all it's solving is making the OS level pc files available.

I looked a bit at what it would take to provide development headers for the rest. I think in 99% of cases, we really only care about udev, so maybe we just have that header and pc file.

I looked at the code, and we should be able to just cherry pick the udev.h from the sources, and generate our own basic .pc file for udev. Maybe I just call this the udev wrapper instead.
The rest of systemd is just so much other stuff, and difficult to build at OS level.