Revert "Allow more generic platform names for linux based platforms."

We need a better solution to find out if we are building on a 64bit system.

This reverts commit 58806890b496aef7c2880e651a8bb73b090cd72a.

Change-Id: I43c48b5cbc5e96f93b65165b0445670a832b0206
Reviewed-by: Jani Heikkinen <jani.heikkinen@digia.com>