build-setup.sh: remove python
build-setup.sh: remove python

Started seeing this with recent fresh builds:

16:24:36 Package python is not available, but is referred to by another package.
16:24:36 This may mean that the package is missing, has been obsoleted, or
16:24:36 is only available from another source
16:24:36 However the following packages replace it:
16:24:36   python2-minimal python2 dh-python 2to3 python-is-python3

Remove python from our build script. This apparently brought in the file
package for free so explicitly include that now.

Tested:
- Verified build-setup.sh can now build the docker image and start a
  bitbake on a system that was not working previously

Change-Id: I00b3398580ada310aa38eed22e7426e059be5e36
Signed-off-by: Andrew Geissler <f7919ac9f8ec0c3ffbc3f483da625c634fd31638@yahoo.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts