Dockerfile: merges manifests builder stages to one (opendatahub-io#1381)

We can combine two build stages into one, as there is no need to
always build both images (not done by podman) to only then decide
from which one we want to copy manifests to the target
image. Instead manifests stage will either copy local manifests or
fetches using the script based on USE_LOCAL argument.

Move USE_LOCAL and OVERWIRTE_MANIFESTS args under FROM since args
have scope of the FROM they are declared in.

It requires opt/manifests directory to exist, but since it's a part
of git repo, it's fine.

Original patch from: Bartosz Majsak <bartosz.majsak@gmail.com> [1]

[1] opendatahub-io#773

Signed-off-by: Yauheni Kaliuta <ykaliuta@redhat.com>
(cherry picked from commit c1671ab)

Dockerfiles/Dockerfile

@@ -1,27 +1,21 @@
 # Build the manager binary
 ARG GOLANG_VERSION=1.21
-ARG USE_LOCAL=false
-ARG OVERWRITE_MANIFESTS=""
 
 ################################################################################
-FROM registry.access.redhat.com/ubi8/go-toolset:$GOLANG_VERSION as builder_local_false
-ARG OVERWRITE_MANIFESTS
-# Get all manifests from remote git repo to builder_local_false by script
+FROM registry.access.redhat.com/ubi8/toolbox as manifests
+ARG USE_LOCAL=false
+ARG OVERWRITE_MANIFESTS=""
 USER root
 WORKDIR /
-COPY get_all_manifests.sh get_all_manifests.sh
-RUN ./get_all_manifests.sh ${OVERWRITE_MANIFESTS}
-
-################################################################################
-FROM registry.access.redhat.com/ubi8/go-toolset:$GOLANG_VERSION as builder_local_true
-# Get all manifests from local to builder_local_true
-USER root
-WORKDIR /opt
-# copy local manifests to build
 COPY opt/manifests/ /opt/manifests/
+COPY get_all_manifests.sh get_all_manifests.sh
+RUN if [ "${USE_LOCAL}" != "true" ]; then \
+        rm -rf /opt/manifests/*; \
+        ./get_all_manifests.sh ${OVERWRITE_MANIFESTS}; \
+    fi
 
 ################################################################################
-FROM builder_local_${USE_LOCAL} as builder
+FROM registry.access.redhat.com/ubi8/go-toolset:$GOLANG_VERSION as builder
 ARG CGO_ENABLED=1
 USER root
 WORKDIR /workspace
@@ -53,7 +47,7 @@ RUN CGO_ENABLED=${CGO_ENABLED} GOOS=linux GOARCH=amd64 go build -a -o manager ma
 FROM registry.access.redhat.com/ubi8/ubi-minimal:latest
 WORKDIR /
 COPY --from=builder /workspace/manager .
-COPY --chown=1001:0 --from=builder /opt/manifests /opt/manifests
+COPY --chown=1001:0 --from=manifests /opt/manifests /opt/manifests
 # Recursive change all files
 RUN chown -R 1001:0 /opt/manifests &&\
     chmod -R g=u /opt/manifests