Can this be merged?

You can use the package as git dependency in mix: https://github.com/joelpaulkoch/sqlite_vec.

I want to refactor the PR so that it doesn't depend on octo_fetch. Instead we can use elixir_make, this way we don't have a runtime dependency and it will integrate better with the ecosystem (cross compilling with burrito, probably also nerves).
I expect this to work pretty good given that we can just reuse the existing Makefile, sqlite-vec.c and sqlite-vec.h.

@joelpaulkoch lmk if I can help with that in anyway! A no-dep Makefile option would be awesome

So, here's the updated PR.
A few notable points:

1. it's not no-dep, but elixir_make is a compile time only dependency, and pretty established (as you can see by the fact that it's in the elixir-lang org on github). It's for instance used by burrito to detect a native library and recompile it when doing cross compilation (that is to say, there are benefits to have elixir_make as dependency compared to manually calling make).
2. To compile the library from the Makefile, we must have Makefile, VERSION, sqlite-vec.c and sqlite-vec.h.tmpl as part of the published package. I solved that by adding symlinks and a publish script which replaces the symlinks with the actual files before publishing the package.
3. I had to update the Makefile so that the install prefix can be set from env.
4. This approach requires that users have make and a c compiler available. There is the concept of precompilers in elixir_make that check for existing binaries to download before compilation but I think it's not quite fitting the scenario here where the native library is not only made for Elixir. So maybe we can later add a step to download from github releases and make the compilation with make and c compiler optional.

Thank you @joelpaulkoch for your hard work here!

One ask — instead of relying on the Makefile + sqlite-vec.h.tmpl from this project, can we instead use the "amalgamation" build, that has pre-processed sqlite-vec.c and sqlite-vec.h files? Here's a sample: https://github.com/asg017/sqlite-vec/releases/download/v0.1.7-alpha.2/sqlite-vec-0.1.7-alpha.2-amalgamation.zip

Hopefully that will mean we don't need to include Makefile/VERSION in here, and maybe avoid the need for the symlinking

Also — do you have a link to docs that talk about the "precompilers" for elixir make? I ask because the sqlite-dist project is for pre-compiling/bundling SQLite extensions for various platforms, so it might be possible to include elixir_make precompiled support in there (which sqlite-vec uses in it's publishing process)

Regarding amalgamation, that would mean we would include those preprocessed files in the package (tarball), right? Then have a simple Makefile to build from sqlite-vec.c and sqlite-vec.h, and no symlinks.
Then, the publishing process would require to first build the amalgamation, then proceed with the Elixir package. I think that would work and avoid symlinking.

Regarding precompilers in elixir_make, it's mentioned here in the docs. If I get it right, it's just an integrated way to compile the native library of an Elixir package and have a known URL for the artifact so that you can first try to download instead of compiling.