CI: move grafana-build into pkg/build (#105640)

* move grafana-build into pkg/build

pkg/build/daggerbuild/containers/exit_error.go

@@ -0,0 +1,29 @@
+package containers
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"dagger.io/dagger"
+)
+
+var (
+	ErrorNonZero = errors.New("container exited with non-zero exit code")
+)
+
+// ExitError functionally replaces '(*container).ExitCode' in a more usable way.
+// It will return an error with the container's stderr and stdout if the exit code is not zero.
+func ExitError(ctx context.Context, container *dagger.Container) (*dagger.Container, error) {
+	container, err := container.Sync(ctx)
+	if err == nil {
+		return container, nil
+	}
+
+	var e *dagger.ExecError
+	if errors.As(err, &e) {
+		return container, fmt.Errorf("%w\nstdout: %s\nstderr: %s", ErrorNonZero, e.Stdout, e.Stderr)
+	}
+
+	return container, err
+}