Include /app/lib/<arch>-linux-gnu directory in LD_LIBRARY_PATH

[nhlfr]

Flatpak supports extending LD_LIBRARY_PATH variable with --env argument - this is a good solution for adding directories like /app/lib/GL.

However, in case of directories like /app/lib/x86_64-linux-gnu or /app/lib/i386-linux-gnu, the problem in extending environment in finish-args is that we lose architecture agnosticism. finish-args cannot be set for a specific architecture.

I have two potential ideas of solving thit issue:

• add /app/lib/<arch>-linux-gnu dir by default to LD_LIBRARY_PATH here

  flatpak/common/flatpak-run.c

  Line 2678 in f6d1a06

  {"LD_LIBRARY_PATH", "/app/lib"},

  - we already know the architecture in flatpak, so that shoudn't be hard
• allow to define finish-args per architecture

I prefer the first solution, because the case of <arch>-linux-gnu directories is so common, that a lot of flatpaks would end with hacking around adding this directory.

[nhlfr]

I would like to work on this, but I would also like to know first what do you think.

cc @alexlarsson

[alexlarsson]

I don't think hardcoding things like that really helps. In particular multilib things, because multilib is not really very useful for flatpak because each arch can just use /lib.

That said, per-arch finish-args seem very useful.

[nhlfr]

OK. What do you think about the following syntax?

"finish-opts": {
  "arch": {
    "x86_64": [
      "--env=LD_LIBRARY_PATH=/app/lib:/app/lib/x86_64-linux-gnu"
    ],
    "i386": [
      "--env=LD_LIBRARY_PATH=/app/lib:/app/lib/i386-linux-gnu"
    ]
  }
}

BTW, my other use case for per-arch finish-args is to use different binaries/packages in --extra-data for every architecture.