Start work on excluding unnecessary CMake modules

[bschwind]

Goals of this PR:

• Reduce the size of the occt-sys crate to below 10 MB, the crates.io upload limit
• Reduce the amount of work CMake needs to do to build opencascade

I realized we can override opencascade files with the CMake BUILD_PATCH variable. I recreated the adm/MODULES directory in our patch directory and verified that CMake picks it up and uses it instead of the file in OCCT.

Next step is to modify adm/MODULES to cut out things we don't need, as well as editing occt-sys/Cargo.toml to exclude big directories that we don't use anyway.

Here's a reference to some of the CMake stuff in occt.

Depends on #112 being merged first.

[strohel]

I realize that this could also be a work-around for CI caching. Once we publish occt-sys to crates.io, we can depend on it through crates.io, including it in the cache (hopefully).

[bschwind]

Once we publish occt-sys to crates.io, we can depend on it through crates.io, including it in the cache (hopefully).

Ah yeah, if that works well then I'd much prefer that approach.

[bschwind]

Trying hard to cut out all unnecessary files to keep the crate size under the 10MB limit - I think we may need a different approach of splitting up toolkits into different crates. I've gotten fairly good at controlling which "toolkits" (as occt calls them) get built, but getting them all to fit in one crate is looking very difficult and time consuming to accomplish.

[strohel]

Issues linked to rust-lang/crates.io#195 seem to be like a good library of workarounds people do to circumvent the limit.

• Perhaps we can do something similar to Use tar.gz image of OpenBLAS blas-lapack-rs/openblas-src#95 ?

[bschwind]

cc @mkovaxx

[bschwind]

@strohel if we specify occt-sys as a git dependency, will our cargo cache action cache it properly? I think we wouldn't be able to publish on crates.io with a git dependency, but maybe it would help with the caching situation?

[bschwind]

Merging this for now, there can be some cleanup afterwards but I want to get this in now to get CI build times down.

[strohel]

Nice!