Add the FRAMEWORKS_BASE_JAVA_SRC_DIRS to aidl includes

only if the module is built against the platform, not the SDK.
Previously it added it if it's doing a platform build.
But we can do an apps_only build inside the platform source tree and
such a build may build modules against the platform.
This fixes the apps build in the platform source tree.

Change-Id: I73e32a8f0e505349790a102321f88e77fba472cd