Use a multistage docker build

Author: monadius

DockerOcamlbuild

@@ -1,4 +1,4 @@
-FROM ocaml/opam:ubuntu-22.04-ocaml-5.0
+FROM ocaml/opam:ubuntu-22.04-ocaml-5.0 AS builder
 
 # Base packages
 RUN set -ex; \
@@ -18,11 +18,42 @@ RUN set -ex; \
     'zarith=1.12' \
     ;
 
-USER opam
-ENV USER=opam
+FROM ubuntu:22.04
 
-RUN sudo mkdir -p /workspace; \
-    sudo chown opam:opam /workspace
-COPY workspace/cwtest.ml /workspace/cwtest.ml
-COPY workspace/cwtest.mli /workspace/cwtest.mli
-COPY workspace/_tags /workspace/_tags
+RUN set -ex; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        gcc \
+        libc6-dev \
+        libgmp-dev \
+    ; \
+    rm -rf /var/lib/apt/lists/*;
+
+COPY --from=builder \
+    /home/opam/.opam/5.0/bin/ocamlc.opt \
+    /home/opam/.opam/5.0/bin/ocamlopt.opt \
+    /home/opam/.opam/5.0/bin/ocamldep.opt \
+    /home/opam/.opam/5.0/bin/ocamlbuild \
+    /home/opam/.opam/5.0/bin/ocamlfind \
+    /home/opam/.opam/5.0/bin/
+
+COPY --from=builder /home/opam/.opam/5.0/lib/ /home/opam/.opam/5.0/lib/
+
+RUN set -ex; \
+    useradd --create-home codewarrior; \
+    mkdir -p /workspace; \
+    chown codewarrior: /workspace;
+
+USER codewarrior
+ENV USER=codewarrior \
+    PATH=/home/opam/.opam/5.0/bin:$PATH
+
+COPY --chown=codewarrior:codewarrior workspace/. /workspace/
+WORKDIR /workspace
+# COPY --chown=codewarrior:codewarrior examples/batteries/. /workspace/
+
+
+# RUN OPAM_SWITCH_PREFIX='/home/opam/.opam/5.0'; export OPAM_SWITCH_PREFIX; \
+#     CAML_LD_LIBRARY_PATH='/home/opam/.opam/5.0/lib/stublibs:/home/opam/.opam/5.0/lib/ocaml/stublibs:/home/opam/.opam/5.0/lib/ocaml'; export CAML_LD_LIBRARY_PATH; \
+#     OCAML_TOPLEVEL_PATH='/home/opam/.opam/5.0/lib/toplevel'; export OCAML_TOPLEVEL_PATH; \
+#     PATH='/home/opam/.opam/5.0/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'; export PATH;