lwt6 constraint for usb (enter_iter_hooks)

Author: raphael-proust

packages/usb/usb.1.3.1/opam

@@ -15,6 +15,10 @@ depends: [
   "conf-pkg-config" {build}
 ]
 
+conflicts: [
+  "lwt" { >= "6~" }
+]
+
 depexts: [
   ["libusb-1.0-0-dev"] {os-family = "debian"}
   ["libusb"] {os-family = "arch"}