app: alternative inner home path

Support binding home to an alternative path in the mount namespace.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/app/system.go

@@ -44,6 +44,8 @@ type appUser struct {
 	// string representation of aid
 	as string
 
+	// home directory host path
+	data string
 	// app user home directory
 	home string
 	// passwd database username