Add flex to build image and VICE preflight check

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.

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Matthias Ladkau
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

SchwertUndMagieOnPebbleCompanionApp/app/src/main/jni/build_vice.sh

@@ -32,7 +32,7 @@ echo "  TOOLCHAIN  : ${TOOLCHAIN} [OK]"
 
 # ---- Ensure required host tools are present ---------------------------------
 MISSING=()
-for tool in dos2unix autoconf automake pkg-config xa; do
+for tool in dos2unix autoconf automake pkg-config xa flex; do
     command -v "$tool" &>/dev/null || MISSING+=("$tool")
 done
 if [ ${#MISSING[@]} -gt 0 ]; then

build-image/Dockerfile

@@ -25,13 +25,14 @@ ENV DEBIAN_FRONTEND=noninteractive \
 # git/unzip/curl/jq: checkout, SDK downloads, and the release workflow's
 # calls to the Gitea API (create release, upload assets).
 # python3-venv: pebble-tool's `sdk install` creates a venv per SDK version.
-# dos2unix/autoconf/automake/pkg-config/xa65/build-essential/gettext: host
-# tools required by the companion app's build_vice.sh (see that file's own
-# preflight check) to cross-compile VICE via autotools before NDK clang
-# takes over for the actual target compilation.
+# dos2unix/autoconf/automake/pkg-config/xa65/build-essential/gettext/flex:
+# host tools required by the companion app's build_vice.sh (see that file's
+# own preflight check, plus flex for VICE's AC_PROG_LEX-based configure) to
+# cross-compile VICE via autotools before NDK clang takes over for the
+# actual target compilation.
 RUN apt-get update && apt-get install -y --no-install-recommends \
         curl ca-certificates git unzip tar xz-utils python3 python3-venv file jq \
-        dos2unix autoconf automake pkg-config xa65 build-essential gettext \
+        dos2unix autoconf automake pkg-config xa65 build-essential gettext flex \
     && rm -rf /var/lib/apt/lists/*
 
 # --- Android SDK: cmdline-tools, platform, build-tools, NDK ---

build-image/VERSION

@@ -1 +1 @@
-1
+2