Use `rsync -aHAX --delete`

[adrienverge]

When creating/restoring cache, the user wants the created files and dir to replace existing ones. This also implies deleting leftover files.

To be clearer, let's take an example with a JS / TypeScript project:

• A project needs to install some "typings" named footypes in node_modules.
• footypes becomes deprecated and should be replaced by footypes2. The developer then replaces footypes with footypes2 in his package.json.
• On next builds, old cache is restored (including node_modules/footypes). Then footypes2 is also installed in node_modules.
• Builds now fail because there are conflicting typings for library foo: both footypes and footypes2 are present.

With the --delete flag added to rsync, when creating new caches, files that are not present in source dir are deleted from target dir.

[mjwwit]

Great addition, thanks!