gerrit: Babeltrace: build only bindings for non-amd64 build

gerrit: Babeltrace: build only bindings for non-amd64 build

Since the python-bindings configuration is a superset of the std
configuration only build the python-bindings for non-amd64 platform.

The reasoning here is that it take much more time on other platform to
build and test than on amd64. Removing the std conf for non-amd64 remove
1 jobs per machine type (from 2).

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>