pkg/specgen: do not depend on libimage for remote

This is the last place were the remote client pulls in libimage, with
this the podman-remote binary size decreases from 44788 KB to
39424 KB (not stripped).

This change simply fixes that by gating it behind the remote build tag.
Of course it would be a bit cleaner to never leak libimage into
pkg/specgen and only have it in pkg/specgen/generate. But this would be
much more involved with big chnages so I went with the easy and quick
way instead.

[NO NEW TESTS NEEDED]

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

pkg/specgen/specgen.go

@@ -6,7 +6,6 @@ import (
 	"strings"
 	"syscall"
 
-	"github.com/containers/common/libimage"
 	nettypes "github.com/containers/common/libnetwork/types"
 	"github.com/containers/image/v5/manifest"
 	"github.com/containers/podman/v4/libpod/define"
@@ -570,20 +569,7 @@ type SpecGenerator struct {
 	ContainerResourceConfig
 	ContainerHealthCheckConfig
 
-	image             *libimage.Image `json:"-"`
-	resolvedImageName string          `json:"-"`
-}
-
-// SetImage sets the associated for the generator.
-func (s *SpecGenerator) SetImage(image *libimage.Image, resolvedImageName string) {
-	s.image = image
-	s.resolvedImageName = resolvedImageName
-}
-
-// Image returns the associated image for the generator.
-// May be nil if no image has been set yet.
-func (s *SpecGenerator) GetImage() (*libimage.Image, string) {
-	return s.image, s.resolvedImageName
+	cacheLibImage
 }
 
 func (s *SpecGenerator) IsInitContainer() bool {

pkg/specgen/specgen_local.go

@@ -0,0 +1,23 @@
+//go:build !remote
+// +build !remote
+
+package specgen
+
+import "github.com/containers/common/libimage"
+
+type cacheLibImage struct {
+	image             *libimage.Image `json:"-"`
+	resolvedImageName string          `json:"-"`
+}
+
+// SetImage sets the associated for the generator.
+func (s *SpecGenerator) SetImage(image *libimage.Image, resolvedImageName string) {
+	s.image = image
+	s.resolvedImageName = resolvedImageName
+}
+
+// Image returns the associated image for the generator.
+// May be nil if no image has been set yet.
+func (s *SpecGenerator) GetImage() (*libimage.Image, string) {
+	return s.image, s.resolvedImageName
+}

pkg/specgen/specgen_remote.go

@@ -0,0 +1,8 @@
+//go:build remote
+// +build remote
+
+package specgen
+
+// Empty stub we do not use any libimage on the remote client,
+// this drastically decreases binary size for the remote client.
+type cacheLibImage struct{}