generalize system SDK inclusion

[slimsag]

Today, we have special build logic in https://github.com/hexops/mach/blob/main/glfw/build.zig which:

• git clones the relevant system SDK repos https://github.com/hexops/sdk-macos-11.3 and https://github.com/hexops/sdk-linux-x86_64 needed to cross-compile GLFW
• Handles asking the user for license agreement, in the case of the MacOS SDK which is distributed under Apple's XCode licensing terms.
• Handles including the relevant directory paths, etc.

This logic is useful outside of just our GLFW bindings, though. For example, it is useful to use this for cross-compiling Google's Dawn WebGPU implementation.

It would also be useful to be able to use this logic outside of Mach entirely, for example to cross compile SDL applications @MasterQ32 ikskuh/SDL.zig#8 - or maybe for @Avokadoen to cross-compile https://github.com/Avokadoen/zig_vulkan perhaps

Idea: Move this logic into a new system_sdk library, so that one can easily import / benefit from this logic.

Challenge: I don't think these SDKs will always include all system libraries, for example the Linux one picks a very specific set of packages - just those required to build Mach. And it would be nice to slim down the MacOS one even further (currently ~164M). Additionally, it's possible that the versions Mach uses are not what others want, or may change over time. So one important thing here will be making it so that people can very easily fork the SDK repos to modify which system libraries are included, and use their fork if preferred - although probably it'll just work fine in most cases.

Question: Does anyone actually want this? Does this sound useful?

[Avokadoen]

Since i am already using the GLFW bindings this would probably be useful for zig_vulkan as well. While we are on the topic, I would also vote to move the GLFW bindings out of the mach repo into its own so it's more apparent for other projects that it's an option to use if you need a window library in zig 👍

Currently zig vulkan cross compile between windows and linux, sadly the only system wide dependency is vulkan which does not support static linking

[slimsag]

While we are on the topic, I would also vote to move the GLFW bindings out of the mach repo into its own so it's more apparent for other projects that it's an option to use if you need a window library in zig 👍

Good point, it would be super nice to have these libraries be in separate repos. At the same time, I am a huge fan of monorepo benefits (a single issue tracker, place to view commit activity, etc.) I will start looking into git subtree, maybe that would give the best of both worlds

[slimsag]

GLFW moved into a separate repo in #42 - it's now at https://github.com/hexops/mach-glfw