conf-clang: update alpine depext (#28290)

* conf-clang: update alpine depext

Seen on #28262

Signed-off-by: Marcello Seri <[email protected]>

* Update packages/conf-clang/conf-clang.2/opam

* Fix os-version

* Fix syntax

* Update packages/conf-clang/conf-clang.2/opam

---------

Signed-off-by: Marcello Seri <[email protected]>

Author: mseri

packages/conf-clang/conf-clang.2/opam

@@ -0,0 +1,30 @@
+opam-version: "2.0"
+maintainer: "https://github.com/ocaml/opam-repository/issues"
+homepage: "https://clang.llvm.org/"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+authors: "The LLVM devs"
+license: "University of Illinois/NCSA Open Source License"
+build: [
+  "clang"
+  "--version"
+]
+depexts: [
+  ["clang"] {os-family = "debian"}
+  ["clang"] {os-family = "ubuntu"}
+  ["clang"] {os-family = "fedora"}
+  ["clang"] {os-distribution = "rhel"}
+  ["clang"] {os-distribution = "centos"}
+  ["clang"] {os-distribution = "alpine" & os-version <= "3.18"}
+  ["clang17"] {os-distribution = "alpine" & os-version >= "3.19" & os-version < "3.21"}
+  ["clang19"] {os-distribution = "alpine" & os-version >= "3.21" & os-version < "3.22"}
+  ["clang20"] {os-distribution = "alpine" & os-version >= "3.22"}
+  ["clang"] {os-family = "suse" | os-family = "opensuse"}
+  ["clang"] {os-distribution = "ol"}
+  ["clang"] {os-distribution = "arch"}
+  # on FreeBSD clang is already part of the base system in contrib/llvm-project/clang
+  ["clang"] {os = "win32"}
+]
+synopsis: "Virtual package relying on clang"
+description:
+  "This package can only install if the clang binary is installed on the system."
+flags: conf