Make docker image smaller

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:latest
+FROM alpine:latest AS builder
 
 ENV OPENTTD_JGR_VERSION=0.65.3
 
@@ -26,18 +26,29 @@ WORKDIR /openttd
 
 RUN git clone --depth 1 --branch jgrpp-$OPENTTD_JGR_VERSION https://github.com/JGRennison/OpenTTD-patches.git source
 
-# Build the source
 WORKDIR /openttd/source
 RUN mkdir build && cd build && \
     cmake .. -DCMAKE_BUILD_TYPE=Release && \
     make -j$(nproc)
 
+FROM alpine:latest
+
 WORKDIR /openttd
+
+COPY --from=builder /openttd/source/build /openttd
+
 RUN mkdir -p /root/.openttd/baseset && \
     wget -q https://cdn.openttd.org/opengfx-releases/7.1/opengfx-7.1-all.zip && \
     unzip opengfx-7.1-all.zip -d /root/.openttd/baseset && \
     rm opengfx-7.1-all.zip
 
+RUN apk add --no-cache \
+    sdl2-dev \
+    fontconfig-dev \
+    icu-dev \
+    lzo-dev
+
 COPY start.sh /start.sh
 RUN chmod +x /start.sh
+
 CMD ["/start.sh"]

start.sh

@@ -1,10 +1,10 @@
-#!/bin/bash
+#!/bin/sh
 SAVE_FILE="/root/.openttd/save/autosave/latest.sav"
 
 if [ -f "$SAVE_FILE" ]; then
     echo "Loading savegame: $SAVE_FILE"
-    exec /openttd/source/build/openttd -D -g autosave/latest.sav
+    exec /openttd/openttd -D -g autosave/latest.sav
 else
     echo "No savegame found. Starting new game."
-    exec /openttd/source/build/openttd -D
+    exec /openttd/openttd -D
 fi