Fix bug: SDK_DIR was not always defined when using T001chain compat layer.
Fix bug: SDK_DIR was not always defined when using T001chain compat layer.

In some cases we go through qibuild/compat BEFORE reading qibuild/general
Everything worked, before the parts where SDK_DIR was explicitely used.

aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild