VICE's configure.ac uses AC_PROG_LEX, which needs flex — missing from
the build image caused a late, confusing "Could not find either flex
or lex!" failure deep inside configure. Add it to the Dockerfile and
to build_vice.sh's own preflight tool check so a missing flex fails
fast with a clear error. Bump build-image/VERSION to 2.
(semver drives Android versionCode/versionName and package.json). The
build-image/ Dockerfile pins the same toolchain for a portable,
containerized Gitea Actions runner (build-image.sh builds and pushes
it) so releases don't depend on any one machine's local setup.
Pushing vX.Y.Z now builds and publishes a Gitea Release automatically.
ml