ccache, save metadata

Dockerfile

@@ -8,6 +8,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     binutils \
     ca-certificates \
     clang \
+    ccache \
     cmake \
     coinor-libipopt-dev \
     curl \
@@ -28,3 +29,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     time \
     tzdata \
     wget
+
+ENV CCACHE_DIR "/cache/ccache"
+
+ARG VCS_URL
+ARG VCS_REF
+LABEL org.opencontainers.image.source=${VCS_URL} `
+      org.opencontainers.image.revision=${VCS_REF}