Enable MemberImportVisibility check on all targets

Author: rnro

Package.swift

@@ -144,3 +144,9 @@ let package = Package(
     ],
     cxxLanguageStandard: .cxx14
 )
+
+for target in package.targets {
+    var settings = target.swiftSettings ?? []
+    settings.append(.enableUpcomingFeature("MemberImportVisibility"))
+    target.swiftSettings = settings
+}