[Docker/alpine]: missing dependency for nokogiri

[kevinnls]

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• [x] Read the contributing instructions
• [x] Update to the latest Gem version (run bundle update github-pages)

This issue affects

• [ ] The site generated by GitHub Pages
• [x] Building sites locally

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What did you do (e.g., steps to reproduce)

1. enable the jemoji plugin in _config.yml
2. make image_alpine
3. SITE=/path/to/site make server

What did you expect to happen?

a running local server

What happened instead?

build failed because the nokogiri gem couldn't access the shared library ld-linux-aarch64.so.1

Additional information

• Nokogiri depends on glibc

  • Linux aarch64-linux (req: glibc >= 2.29) including musl/Alpine - Nokogiri docs on supported platforms

• From the Nokogiri docs on musl having error loading shared library

  Musl-based systems like Alpine may not have a glibc-compatible library installed, leading to problems running the precompiled native gems.

• and also the solution

  Install the glibc compatibility layer: apk add gcompat

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NB this does not affect the image built from Dockerfile.alpine@e9d9768.

However I feel it would be nice to include the required library in the image because

• emoji are used quite often while blogging today
• most users of the Docker images are likely to prefer the Alpine one for local development thanks to it's smaller size on disk