Incompatibility with Podman: "attempted to redefine 'BUILDPLATFORM'" Error in Multi-Stage Build

[frobware]

I'm encountering an issue when building the bpfman-operator and bpfman-agent image using Podman. The build fails with the following error message:

% make build-images
Adding GOCACHE volume mount /home/aim/.cache/go-build:/root/.cache/go-build.
podman version
Client:       Podman Engine
Version:      5.2.1
API Version:  5.2.1
Go Version:   go1.22.5
Built:        Wed Aug 14 01:00:00 2024
OS/Arch:      linux/amd64
podman buildx build --load -t quay.io/bpfman/bpfman-operator:latest \
  --build-arg TARGETPLATFORM=linux/amd64 \
  --build-arg TARGETARCH=amd64 \
  --build-arg BUILDPLATFORM=linux/amd64 \
  --volume "/home/aim/.cache/go-build:/root/.cache/go-build:z" \
  -f Containerfile.bpfman-operator .
Error: reading multiple stages: attempted to redefine "BUILDPLATFORM": invalid argument

This issue arises due to the redefinition of the BUILDPLATFORM argument in the Containerfile.bpfman-operator (and in Containerfile.bpfman-agent. The Containerfile* currently defines ARG BUILDPLATFORM twice: once globally at the top of the file and again within the bpfman-operator-build stage. While Docker allows this without issue, Podman is stricter about argument redefinition, resulting in a build failure.

Steps to Reproduce:

1. Use Podman version 5.2.1 (or similar).
2. Run make build-images OCI_BIN=podman.
3. The build fails with the error mentioned above.

If I use docker the build completes OK:

% make build-images OCI_BIN=docker
docker version
Client: Docker Engine - Community
 Version:           27.1.2
 API version:       1.46
 Go version:        go1.21.13
 Git commit:        d01f264
 Built:             Mon Aug 12 11:52:28 2024
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          27.1.2
  API version:      1.46 (minimum version 1.24)
  Go version:       go1.21.13
  Git commit:       f9522e5
  Built:            Mon Aug 12 11:50:46 2024
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.20
  GitCommit:        8fc6bcff51318944179630522a095cc9dbf9f353
 runc:
  Version:          1.1.13
  GitCommit:        v1.1.13-0-g58aa920
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
docker buildx build --load -t quay.io/bpfman/bpfman-operator:latest \
  --build-arg TARGETPLATFORM=linux/amd64 \
  --build-arg TARGETARCH=amd64 \
  --build-arg BUILDPLATFORM=linux/amd64 \
   \
  -f Containerfile.bpfman-operator .
[+] Building 0.5s (3/4)                                                                                                                                           docker-container:admiring_germain
 => [internal] load build definition from Containerfile.bpfman-operator                                                                                                                        0.0s
 => => transferring dockerfile: 2.17kB                                                                                                                                                         0.0s
 => WARN: RedundantTargetPlatform: Setting platform to predefined $TARGETPLATFORM in FROM is redundant as this is the default behavior (line 33)                                               0.0s
 => [internal] load metadata for quay.io/fedora/fedora-minimal:latest                                                                                                                          0.4s
 => [internal] load metadata for docker.io/library/golang:1.22                                                                                                                                 0.4s
 => [auth] library/golang:pull token for registry-1.docker.io   
...                        

Expected Behaviour:

The image should build successfully without errors, as it does when using Docker.

Proposed Solution:

To resolve this issue, I suggest removing the global ARG BUILDPLATFORM=linux/amd64 declaration at the top of the Containerfile.bpfman-{agent,operator}. This will allow the build process to pass in the BUILDPLATFORM value as needed without causing a conflict.