Rename distro-style CI build from "release" to "production"

This avoids confusion with the meaning of "release" used by
AX_IS_RELEASE. AX_IS_RELEASE is about facts about the source tree,
namely the distinction between releases (tags) and random snapshots.
The build variants in .travis.yml are about facts about the build
being done, namely the distinction between production and
debug/developer builds.

Production builds are sometimes referred to as "release builds",
for example in typical CMake and MSVC build environments, but a
different term seems better here.

Signed-off-by: Simon McVittie <smcv@debian.org>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=97357

.travis.yml

@@ -46,7 +46,7 @@ script:
   - PYTHON=/usr/bin/python dbus_ci_parallel=2 dbus_ci_sudo=yes ./tools/ci-build.sh
 
 env:
-  - dbus_ci_variant=release
+  - dbus_ci_variant=production
   - dbus_ci_variant=debug
   - dbus_ci_variant=reduced
   - dbus_ci_variant=legacy

tools/ci-build.sh

@@ -4,7 +4,7 @@ set -e
 set -x
 
 if [ -z "$dbus_ci_variant" ]; then
-	dbus_ci_variant=release
+	dbus_ci_variant=production
 fi
 
 if [ -z "$dbus_ci_host" ]; then
@@ -74,7 +74,7 @@ case "$dbus_ci_buildsys" in
 				# an older system or one that does not have
 				# all the optional libraries.
 				set _ "$@"
-				# No LSMs (the release build has both)
+				# No LSMs (the production build has both)
 				set "$@" --disable-selinux --disable-apparmor
 				# No inotify (we will use dnotify)
 				set "$@" --disable-inotify