Add webp to developing box.

Add missing defines.

Update script to match latest IM7.

Add relevant info.

Add note for both NixOS users.

Merge branch 'explicit_feature_flag'

Some C compilers don't like trailing slash in comments.

Don't copy shell.nix to avoid being confused by changes to it not being picked up.

Add more manageable way of managing version based feature flags.

Fix getConfigureOptions in the testing container

Fix fontconfig error in NixOS container

Add NixOS test environment

Add user location check for ImageMagick 7

Add helper file.

Fix incorrect directory name.

Tweak build list to not build against 8 until that branch has been merged.

Typo.

Remove inappropriate setting.

ImageMagick changed main branch name.

Add basic test for 2 versions, to avoid triggering 120 builds when a typo will cause all of them to fail.

Run on all branches.

Rename action.

Disable undesirable bit of action.

Update .github/workflows/run-tests.yml

Co-authored-by: Alexis Saettler <alexis@saettler.org>

add step for uploading artifacts

make sure the imagemagick version variable is correctly shown