[hooks] Exclude a platform from being built by dependency's build hook

[HosseinYousefi]

package:jni supports Windows, Linux, ... and Android but a lot of the times users only want to use it for Android. Sentry also supports Windows, Linux, ... but wants to use package:jni only on Android. However right now if someone wants to build an app that depends on Sentry, they still need to have JDK installed on their machine: https://github.com/getsentry/sentry-dart/issues/3033

This is a problem in the Flutter plugin build system as well: https://github.com/flutter/flutter/issues/81650

With build hooks, we could allow end-users to add some user-defines for package:jni not to be built for Desktop but this means that a Sentry user has to know about the internal implementation of Sentry which is not ideal. Ideally we would want Sentry itself to be able to specify this.