uring.0.1: Fix license field syntax and accept failures on old distri…

…butions (default C compiler does not support stdatomic.h)

packages/uring/uring.0.1/opam

@@ -4,7 +4,7 @@ description:
   "Bindings to the Linux io_uring kernel IO interfaces. See https://github.com/ocaml-multicore/eio for a higher-level API using this."
 maintainer: ["[email protected]"]
 authors: ["Anil Madhavapeddy" "Sadiq Jaffer" "Thomas Leonard"]
-license: "(ISC AND MIT)"
+license: ["ISC" "MIT"]
 homepage: "https://github.com/ocaml-multicore/ocaml-uring"
 bug-reports: "https://github.com/ocaml-multicore/ocaml-uring/issues"
 depends: [
@@ -25,6 +25,10 @@ depends: [
   "alcotest" {>= "1.4.0" & with-test}
   "odoc" {with-doc}
 ]
+x-ci-accept-failures: [
+  "centos-7" # default C compiler does not support stdatomic.h
+  "oraclelinux-7" # default C compiler does not support stdatomic.h
+]
 build: [
   ["dune" "subst"] {dev}
   [