BinariesTarball inherits unused extra_options from Tarball

[VRehnberg]

The Tarball EasyBlock defines two extra_options install_type and preinstall_cmd. Besides a log message in run, the only place both are used is in the install_step.

So far it is perfectly fine. However, the BinariesTarball inherits the extra_options but overrides the install_step. Thus, the extra_options inherited from Tarball does nothing when used with BinariesTarball.

This behaviour was confusing to me as that is not what is stated in the documentation.

I see two possible solutions:

1. Rewrite the easyblocks such that BinariesTarball uses the extra_options.
   2 .Override extra_options in BinariesTarball to remove unused extra_options.

As I found this issue when I was trying use preinstall_cmd I would prefer 1. If you agree that this is a bug I could probably write up a PR.

[smoors]

i agree it's a bug

would be good to reorganize Tarball a bit into so that the logic around install_type and preinstall_cmd doesn't have to be duplicated in BinariesTarball