Add support for building OBI with Podman (#797)

* Make build work with podman

* Make OCI_BIN the default for OTEL_EBPF_GENFILES_OCI_BIN

Author: fstab

cmd/obi-genfiles/obi_genfiles.go

@@ -36,8 +36,9 @@ type config struct {
 	ContainerPrefix string `env:"OTEL_EBPF_GENFILES_CONTAINER_PREFIX" envDefault:"/__w/"`
 	HostPrefix      string `env:"OTEL_EBPF_GENFILES_HOST_PREFIX"      envDefault:"/home/runner/work/"`
 	Package         string `env:"OTEL_EBPF_GENFILES_PKG"              envDefault:"go.opentelemetry.io/obi/pkg/obi"`
-	OCIBin          string `env:"OTEL_EBPF_GENFILES_OCI_BIN"          envDefault:"docker"`
+	GenFilesOCIBin  string `env:"OTEL_EBPF_GENFILES_OCI_BIN"`
 	GenImage        string `env:"OTEL_EBPF_GENFILES_GEN_IMG"`
+	OCIBin          string `env:"OCI_BIN"                             envDefault:"docker"`
 }
 
 var cfg config
@@ -448,16 +449,22 @@ func runInContainer(wd string) {
 		fmt.Println("adjusted wd:", adjustedWD)
 	}
 
-	currentUser, err := user.Current()
-	if err != nil {
-		bail(fmt.Errorf("error getting current user id: %w", err))
+	args := make([]string, 0, 10)
+	args = append(args, "run", "--rm")
+	if strings.HasSuffix(cfg.GenFilesOCIBin, "podman") {
+		args = append(args, "--userns=keep-id")
+	} else {
+		currentUser, err := user.Current()
+		if err != nil {
+			bail(fmt.Errorf("error getting current user id: %w", err))
+		}
+		args = append(args, "--user", currentUser.Uid+":"+currentUser.Gid)
 	}
+	args = append(args, "-v", adjustedWD+":/src:z")
+	args = append(args, "-e", "OTEL_EBPF_GENFILES_MODIFIED_ONLY="+strconv.FormatBool(cfg.GenModifiedOnly))
+	args = append(args, cfg.GenImage)
 
-	err = executeCommand(cfg.OCIBin, "run", "--rm",
-		"--user", currentUser.Uid+":"+currentUser.Gid,
-		"-v", adjustedWD+":/src",
-		"-e", "OTEL_EBPF_GENFILES_MODIFIED_ONLY="+strconv.FormatBool(cfg.GenModifiedOnly),
-		cfg.GenImage)
+	err := executeCommand(cfg.GenFilesOCIBin, args...)
 	if err != nil {
 		bail(fmt.Errorf("error waiting for child process: %w", err))
 	}
@@ -557,6 +564,9 @@ func main() {
 	if err := env.Parse(&cfg); err != nil {
 		bail(fmt.Errorf("error loading config: %w", err))
 	}
+	if len(cfg.GenFilesOCIBin) == 0 {
+		cfg.GenFilesOCIBin = cfg.OCIBin
+	}
 
 	wd, err := moduleRoot()
 	if err != nil {