Experimental support for FreeBSD added to rebuilderd

[cen]

Hello

after a few weeks of hacking I managed to add very 
early/experimental/alpha support for FreeBSD to rebuilderd.

The initial builds are in progress and look quite decent: 
https://rebuilderd.xpam.pl:2096/

I am currently rebuilding the ports tree for fBSD 15.

Since the upstream is currently not technically reproducible I had to 
relax the bit-for-bit identical requirement of rebuilderd.

I consider the pkg to be reproducible if the tar is content-identical 
(via diffoscope), ignoring timestamps and some of the manifest files.


Two immediate issues are:

- upstream not setting SDO

- short commit tag length in manifest files can vary depending on port 
tree clone depth (reported and already fixed in poudriere)

- no snapshot repo, however, I did a few tricks to try and minimize that 
issue for now.

I'm still early in the rebuild process so I'll do more statistical 
analysis on the failures when more ports go through the rebuild.


I'll go into more technical details at a later point, but if there are 
any FreeBSD experts on this ML I'd love to engage and review my approach.


In unrelated news, I have added arm64 to my Debian SID rebuilder.


Next focus is stability and some upstreaming work.


Best regards
cen1 / Klemen