Out-of-tree builds against the GSL

🚀 Feature

It would be great to be able to do out-of-tree builds of packages that depend on libraries such as the GSL, which are currently not included in the xbuildenv:

https://github.com/pyodide/pyodide/blob/fdf39f89efe0308ee091e884c151ce57fbe3168f/pyodide-build/pyodide_build/create_xbuildenv.py#L59-L64

Motivation

I’m trying to setup an out-of-tree CI build of the latest version of galpy (see #2676), but it requires the GSL to build and this does not appear to be included in the xbuildenv. So the CI job fails:

https://github.com/jobovy/galpy/runs/7958109347?check_suite_focus=true#step:6:546

Pitch

Perhaps it makes sense to have two out-of-tree xbuildenv environments: a small one like the current one and one that includes the full WASM_LIBRARY_DIR for people who need additional libraries. 180 MB of WASM_LIBRARY_DIR is not small, but easily cached in CI jobs.

Alternatives

Just add the GSL to the xbuildenv.

[hoodmane]

Thanks @jobovy! This was a helpful discussion. After #3109 is merged we can add a section on static libraries.

[jobovy]

Okay, I tried this and it seems to have built in ~3min.: https://github.com/jobovy/galpy/actions/runs/3063192094/jobs/4944996224. I’ll have to take a look at the artifact later to see whether the wheel is actually correct. Thanks!