Update nix flake

[raboof]

Not yet functional:

warning: Git tree '/home/aengelen/dev/vulnerablecode' is dirty
error: builder for '/nix/store/mcyd7cfny2p4rzlfax3kwypn5a03ihv2-mach_nix_file.drv' failed with exit code 1;
       last 10 log lines:
       > Mach-nix version: master
       > Python: 3.8.5
       > Cause: Requirements conflict: cryptography (<SpecifierSet('==36.0.2')>,)
       > The requirements which caused the error:
       >   cryptography (<SpecifierSet('==36.0.2')>,)
       >
       > The given requirements might contain package versions which are not yet part of the dependency DB
       > currently used. The DB can be updated by specifying 'pypiDataRev' when importing mach-nix.
       > For examples see: https://github.com/DavHau/mach-nix/blob/master/examples.md
       >
       For full logs, run 'nix log /nix/store/mcyd7cfny2p4rzlfax3kwypn5a03ihv2-mach_nix_file.drv'.
(use '--show-trace' to show detailed location information)

[pombredanne]

Thanks!

[TG1999]

@raboof thanks for your contribution, please add your sign-off DCO is failing.

[raboof]

@raboof thanks for your contribution, please add your sign-off DCO is failing.

I didn't yet because it's a non-functioning draft PR, but I guess I can sign the DCO to make explicit that I'm happy for anyone to take this as a starting point and continue. Not worth merging yet IMHO.

[pombredanne]

@raboof Hey... ping! will you want us to merge this?

[raboof]

Hey - it was great to meet in Brussels!

Unfortunately it looks like this PR is still not quite functional. I think we should probably abandon this PR and replace mach-nix with 'manual' nix packaging or dream2nix.