binary addons: fix dependency handling for dependencies

I noticed that there are currently two errors in how we handle dependencies of binary addon dependencies in cmake.
* There's a typo on line 111 i.e. the `}` before the `)` at the end of the line is wrong and results in dependency handling not working.
* Apparently `DEPENDS` of cmake's `externalproject_add()` only works for targets that are already known (i.e. have already been processed by cmake) but this might not always be the case for us so we better use `add_dependencies()` instead.

We are currently not really using this with the audioencoder addons (because linux/osx/android uses depends and win32 uses pre-built dependencies) but we might need it later.