bake: fix entitlements path checks for local outputs

Previous check based on dest attributes was not correct
as the attributes already get converted before validation happens.

Because the local path is not preserved for single-file
outputs and gets replaced by io.Writer, a temporary array variable
was needed. This value should instead be added to ExportEntry
struct in BuildKit in future revision.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit c6e403ad7f)

controller/build/build.go

@@ -93,7 +93,7 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in *controllerapi.Buil
 	}
 	opts.Session = append(opts.Session, ssh)
 
-	outputs, err := controllerapi.CreateExports(in.Exports)
+	outputs, _, err := controllerapi.CreateExports(in.Exports)
 	if err != nil {
 		return nil, nil, nil, err
 	}