build: add the deploydir target for gitian

This is a helper target that stops just before the creation of the dmg.
build: Clean up the dmg layout
build: add a deterministic dmg signer
docs: add/update docs for osx dmg signing
Merge pull request #5363

7a9cf80 docs: add/update docs for osx dmg signing (Cory Fields)
914868a build: add a deterministic dmg signer (Cory Fields)
d69ed2b build: Clean up the dmg layout (Cory Fields)
2f327a3 build: add the deploydir target for gitian (Cory Fields)