manifest: add ostree mount to stages in OSTreeDeployment

Stages that modify files in the ostree deployment need the sysroot
bindmount for any changes to take effect.
Adding the mount to the keymap and locale stages since they need to
modify files in /etc.

internal/manifest/commit_deployment.go

@@ -160,6 +160,7 @@ func (p *OSTreeDeployment) serialize() osbuild.Pipeline {
 			Keymap: p.Keyboard,
 		}
 		keymapStage := osbuild.NewKeymapStage(options)
+		keymapStage.MountOSTree(p.osName, p.osTreeRef, 0)
 		pipeline.AddStage(keymapStage)
 	}
 
@@ -168,6 +169,7 @@ func (p *OSTreeDeployment) serialize() osbuild.Pipeline {
 			Language: p.Locale,
 		}
 		localeStage := osbuild.NewLocaleStage(options)
+		localeStage.MountOSTree(p.osName, p.osTreeRef, 0)
 		pipeline.AddStage(localeStage)
 	}