Do not build qcheck tests on OCaml 5

The expect test hardcode the RNG behavior of OCaml 4 and thus lead to
thousands of lines of failures.

Short excerpt:

    #=== ERROR while compiling qcheck.0.18 ========================================#
    # context              2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.5.0.0 | file:///home/opam/opam-repository
    # path                 ~/.opam/5.0/.opam-switch/build/qcheck.0.18
    # command              ~/.opam/opam-init/hooks/sandbox.sh build dune runtest -p qcheck -j 47
    # exit-code            1
    # env-file             ~/.opam/log/qcheck-7-cf6045.env
    # output-file          ~/.opam/log/qcheck-7-cf6045.out
    ### output ###
    # File "example/output.txt.expected", line 1, characters 0-0:
    # /usr/bin/git --no-pager diff --no-index --color=always -u _build/default/example/output.txt.expected _build/default/example/output.txt
    # diff --git a/_build/default/example/output.txt.expected b/_build/default/example/output.txt
    # index 2bcc615..ce4682e 100644
    # --- a/_build/default/example/output.txt.expected
    # +++ b/_build/default/example/output.txt
    # @@ -2,13 +2,13 @@ random seed: 1234
    #
    #  --- Failure --------------------------------------------------------------------
    #
    # -Test should_fail_sort_id failed (18 shrink steps):
    # +Test should_fail_sort_id failed (12 shrink steps):
    #
    #  [1; 0]
    #
    #  === Error ======================================================================
    #
    # -Test should_error_raise_exn errored on (63 shrink steps):
    # +Test should_error_raise_exn errored on (62 shrink steps):
    #
    #  0
    #
    # @@ -19,59 +19,59 @@ exception Dune__exe__QCheck_runner_test.Error
    #
    #  Collect results for test collect_results:
    #
    # -4: 20 cases
    # -3: 25 cases
    # -2: 17 cases
    # -1: 18 cases
    # -0: 20 cases
    # +4: 24 cases
    # +3: 20 cases
    # +2: 18 cases
    # +1: 21 cases
    # +0: 17 cases

Author: Leonidas-from-XIV

packages/qcheck/qcheck.0.18.1/opam

@@ -12,7 +12,7 @@ tags: [
 build: [
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "build" "@doc" "-p" name "-j" jobs] {with-doc}
-  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test & ocaml:version < "5.0.0"}
 ]
 depends: [
   "dune" { >= "2.2" }

packages/qcheck/qcheck.0.18/opam

@@ -12,7 +12,7 @@ tags: [
 build: [
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "build" "@doc" "-p" name "-j" jobs] {with-doc}
-  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test & ocaml:version < "5.0.0"}
 ]
 depends: [
   "dune" { >= "2.2" }

packages/qcheck/qcheck.0.19/opam

@@ -23,7 +23,7 @@ conflicts: [
 build: [
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "build" "@doc" "-p" name "-j" jobs] {with-doc}
-  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test & ocaml:version < "5.0.0"}
 ]
 dev-repo: "git+https://github.com/c-cube/qcheck.git"
 url {
@@ -32,4 +32,4 @@ url {
     "md5=6913306eb3065da1dee749d67732cb01"
     "sha512=ab77384e64887c4c88d6e641f433709a83bafc7cd2d05d548fdfee3593beb3bc5c4345db03e324e033ecd4fd2ae600fa92cea3e5753d5e322d13a01ba787eeb6"
   ]
-}
+}