Dockerfile: fix duplicate WORKDIR, and source COPY for update-modules…

… stage

I noticed that building the "vendor" target was copying the source twice;
once in the "build-base" stage, and once in the "update-modules" stage:

    docker buildx bake --set vendor.args.MODULE=github.com/docker/cli vendor
    ...
    => [build-base 1/3] COPY --from=hugo /go/bin/hugo /bin/hugo                 0.2s
    => [build-base 2/3] COPY --from=node /src/node_modules /src/node_modules    1.6s
    => [build-base 3/3] COPY . .                                                3.1s
    => [update-modules 1/4] WORKDIR /src                                        0.0s
    => [update-modules 2/4] COPY . .                                            5.0s
    => [update-modules 3/4] RUN hugo mod get -u                                14.1s
    => [update-modules 4/4] RUN hugo mod vendor                                17.3s

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Dockerfile

@@ -48,8 +48,6 @@ RUN htmltest
 
 FROM build-base as update-modules
 ARG MODULE="-u"
-WORKDIR /src
-COPY . .
 RUN hugo mod get ${MODULE}
 RUN hugo mod vendor