In preparation for switching to auto-generated dockerfiles, remove the
FEATURES env variable. The equivalent functionality can be achieved in
most cases by just looking for existance of a binary.

The cases which don't correspond to binaries are simply dropped because
configure/meson will probe for any requested feature anyway.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210623142245.307776-6-berrange@redhat.com>
Message-Id: <20210709143005.1554-14-alex.bennee@linaro.org>