CI: Cache the built node

[electrumsv]

CI: Cache the built node

[rt121212121]

This would likely require:

• The cache directory being the extracted built objects that the package will include.
• The build process being changed to move the objects there.
• The setup.py script using this new cached object directory and skipping the build if it were present, rather than the cloned repo directory.
• The build scripts taking in an extra argument representing the revision to build (revision is a fixed hash which a tag is not).
• The cache key using the build revision and OS as part of it for uniqueness.

[rt121212121]

The plan was flawed. It can't possibly pull in the dependencies unless they are already present, and building Boost is part of the Linux build process this would skip.

• See issue #15 for Linux.
• Revisit all the build caching so that Windows and MacOS have the dependencies installed for auditwheel and delocate to pull in.