Improve build script

[janhoy]

In #104 I moved the build.sh script from requiring a local python and pelican install, to using a docker image locally.

The script has some weaknesses and bugs.

• The chained commands pip and pelican were not passed correctly to docker runtime, causing error
  ./build.sh: line 64: pelican: command not found
• The requirements needed to be pulled every single time

This PR addresses this

• On first run, check if a local image solr-pelican-image is present. If not, build the image. If it exists, use it as-is
• Re-build image if requirements.txt is newer than latest image build time
• Add proper getopts argument parsing with pass-through of options to pelican (e.g. -v for verbose)
• Uses python:3-alpine as image, smaller and no need for preinstalled pelican v4.8.0

This all makes for a much faster workflow and less waste of bandwidth.

[janhoy]

The script is tested on MacOS Sonoma 14.5, and I just tested it on Debian as well.

If anyone have a Linux box or WSL2 Windows box to test on, that would be perfect.

[gerlowskija]

LGTM. I don't have a Windows/WSL box to test on unfortunately, but can give another +1 for it working on Mac.

[janhoy]

Thanks for the review. I tried running WSL2 on my M1 mac, and I got all the way to installing Win11 arm in UTM/QEmu, but then it would not allow nested virtualization, so wsl could not be installed. Well.