Add patches to ocaml-variants 4.09 to fix compilation with gcc 11.2

[MisterDA]

Follow-up to 9d1dfdcd28ab617f41a962895d5f284fe15b86dc where ocaml-variants were forgotten. See also #21786.

This error was triggered while building variants for ocaml 4.09.1 with Apline 3.16 in ocaml-ci, see for instance: https://images.ci.ocaml.org/job/2022-10-13/165209-ocluster-build-1c30ec#L1256.

The PR was generated with

cat >opam.patch <<EOF
diff --git a/packages/ocaml-variants/ocaml-variants.4.09.1+32bit/opam b/packages/ocaml-variants/ocaml-variants.4.09.1+32bit/opam
index 7e496074ba..a6024dd1ba 100644
--- a/packages/ocaml-variants/ocaml-variants.4.09.1+32bit/opam
+++ b/packages/ocaml-variants/ocaml-variants.4.09.1+32bit/opam
@@ -55,8 +55,11 @@ post-messages: [
 ]
 available: !(os = "macos" & arch = "arm64")
 license: "LGPL-2.1-or-later WITH OCaml-LGPL-linking-exception"
-patches: ["alt-signal-stack.patch"]
+patches: ["alt-signal-stack.patch" "0001-Re-generate-configure.patch"]
 extra-source "alt-signal-stack.patch" {
   src: "https://github.com/ocaml/ocaml/commit/8eed2e441222588dc385a98ae8bd6f5820eb0223.patch"
   checksum: "sha256=a76506f98450971c954d9322344da592dbf1c38e5bca91ec75c4f9c2889ba637"
 }
+extra-files: [
+  ["0001-Re-generate-configure.patch" "md5=3e01b702dcdce9e5fc41f7eb66290501"]
+]
EOF

for variant in ocaml-variants/ocaml-variants.4.09.1*; do
  mkdir -p "$variant/files"
  cp "ocaml-base-compiler/ocaml-base-compiler.4.09.1/files/0001-Re-generate-configure.patch" "$variant/files"
  patch -p1 "$variant/opam" opam.patch
done

rm -f opam.patch

cc @AltGr @dra27 @kit-ty-kate.