fix: compile unrar from source (package not available in Alpine repos)

Dockerfile

@@ -1,10 +1,15 @@
 FROM alpine:latest
 LABEL maintainer="Julien Cabillot <dockerimages@cabillot.eu>"
 
-RUN apk add --no-cache unrar && \
-    rm -rf /usr/lib/ruby/gems/*/cache/* \
-        /var/cache/apk/* \
-        /tmp/* \
-        /var/tmp/*
+RUN apk add --no-cache wget g++ make && \
+    wget -q "https://www.rarlab.com/rar/unrarsrc-7.1.4.tar.gz" -O /tmp/unrar.tar.gz && \
+    tar xzf /tmp/unrar.tar.gz -C /tmp && \
+    cd /tmp/unrar && \
+    make -j$(nproc) && \
+    make install && \
+    cd / && \
+    rm -rf /tmp/unrar* && \
+    apk del wget g++ make && \
+    rm -rf /var/cache/apk/* /tmp/* /var/tmp/*
 
-ENTRYPOINT [ "/bin/sh", "-c", "cd /data && /usr/bin/unrar" ]
+ENTRYPOINT [ "/bin/sh", "-c", "cd /data && /usr/local/bin/unrar" ]