scons: Delete the ALPHA default build configuration.

Change-Id: Ifbc0b6dd9b85e5a00ab11f16b2703b4ae946207e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24645
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
5 files changed