macdeploy: consolidate .DS_Store generation

Rather than two lots of logic doing roughly the same thing, dependent on if
you're compiling on Linux or macOS, combine the .DS store generation into
macdeployqtplus.

This also removes the -fancy and -volname options.

contrib/macdeploy/README.md

@@ -6,11 +6,7 @@ The `macdeployqtplus` script should not be run manually. Instead, after building
 make deploy
 ```
 
-During the deployment process, the disk image window will pop up briefly
-when the fancy settings are applied. This is normal, please do not interfere,
-the process will unmount the DMG and cleanup before finishing.
-
-When complete, it will have produced `Bitcoin-Qt.dmg`.
+When complete, it will have produced `Bitcoin-Core.dmg`.
 
 ## SDK Extraction
 
@@ -111,7 +107,7 @@ broken. Only the compression feature is currently used. Ideally, the creation co
 and `genisoimage` would no longer be necessary.
 
 Background images and other features can be added to DMG files by inserting a
-`.DS_Store` before creation. This is generated by the script `contrib/macdeploy/custom_dsstore.py`.
+`.DS_Store` during creation.
 
 As of OS X 10.9 Mavericks, using an Apple-blessed key to sign binaries is a requirement in
 order to satisfy the new Gatekeeper requirements. Because this private key cannot be