makebuildserver: remove platforms/build-tools considered obsolete
makebuildserver: remove platforms/build-tools considered obsolete

They can still be installed pre-build when required via sdkmanager.
Not many apps would need them nowadays.

f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver