Merge pull request ocaml#27290 from toots/patch-12

Fix conf-mad check for freebsd

Author: shonfeder

packages/conf-mad/conf-mad.2/opam

@@ -0,0 +1,25 @@
+opam-version: "2.0"
+maintainer: "https://github.com/ocaml/opam-repository/issues"
+homepage: "https://www.underbit.com/products/mad/"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+authors: "mad dev team"
+license: "GPL-2.0-only"
+build: [
+  ["pkg-config" "--exists" "mad"]
+]
+depends: [
+  "conf-pkg-config" {build}
+]
+depexts: [
+  ["libmad-dev"] {os-distribution = "alpine"}
+  ["libmad"] {os-distribution = "arch" | os-distribution = "nixos"}
+  ["libmad-devel"] {os-distribution = "centos" | os-distribution = "fedora" | os-family = "suse" | os-family = "opensuse"}
+  ["libmad0-dev"] {os-family = "debian" | os-family = "ubuntu"}
+  ["libmad"] {os = "win32" & os-distribution = "cygwinports"}
+  ["mad"] {os = "macos" & os-distribution = "homebrew"}
+  ["libmad"] {os = "freebsd"}
+]
+synopsis: "Virtual package relying on mad"
+description:
+  "This package can only install if the mad library is installed on the system."
+flags: conf