redhat: set LC_ALL=C before sorting config content
Bugzilla: INTERNAL
Upstream Status: RHEL-only
Tested: make rh-configs-prep LC_ALL=C vs make rh-configs-prep LC_ALL=en_US.UTF-8
generate the same config file
The content of generated config files is sorted in build_configs.sh.
This gives unpredictable output if different locale is set.
Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>