apt: ignore cache for "apt update"

"apt update" should never be cached.
This also shouldn't break caching for anything run after it unless the
rootfs changed (ie. apt cache was actually updated).

Signed-off-by: Brian Goff <[email protected]>

Author: cpuguy83

pkg/pkgmgr/dpkg.go

@@ -237,7 +237,11 @@ func (dm *dpkgManager) unpackAndMergeUpdates(ctx context.Context, updates types.
 	)
 
 	// Run apt update && apt download list of updates to target folder
-	updated := toolingBase.Run(llb.Shlex("apt update"), llb.WithProxy(utils.GetProxy())).Root()
+	updated := toolingBase.Run(
+		llb.Shlex("apt update"),
+		llb.WithProxy(utils.GetProxy()),
+		llb.IgnoreCache,
+	).Root()
 
 	// Download all requested update packages without specifying the version. This works around:
 	//  - Reports being slightly out of date, where a newer security revision has displaced the one specified leading to not found errors.