CI: add Dockerfile for repochecker (used for student's CI)

Dockerfile-repochecker

@@ -0,0 +1,21 @@
+FROM golang:alpine as gobuild
+
+RUN apk add --no-cache git
+
+WORKDIR /go/src/srs.epita.fr/fic-server/
+
+ADD go.mod go.sum ./
+ADD settings settings/
+ADD libfic ./libfic/
+ADD admin ./admin/
+ADD repochecker ./repochecker/
+
+RUN go get -d -v ./repochecker
+RUN go build -v -o repochecker/repochecker ./repochecker
+
+
+FROM alpine
+
+ENTRYPOINT ["/usr/bin/repochecker"]
+
+COPY --from=gobuild /go/src/srs.epita.fr/fic-server/repochecker/repochecker /usr/bin/repochecker