Merge pull request #4986 from kit-ty-kate/windows-ci-fix

[2.1 backport] Speed up and fix AppVeyor runs

Makefile

@@ -267,4 +267,4 @@ cold-%:
 
 .PHONY: run-appveyor-test
 run-appveyor-test:
-	env PATH="`pwd`/bootstrap/ocaml/bin:$$PATH" ./appveyor_test.sh
+	env -u OCAMLLIB -u CAML_LD_LIBRARY_PATH PATH="`pwd`/bootstrap/ocaml/bin:$$PATH" ./appveyor_test.sh

appveyor.yml

@@ -7,11 +7,13 @@ environment:
   global:
     CYG_ROOT: cygwin64
     CYG_ARCH: x86_64
+    CYGWIN: winsymlinks:native
     OCAML_PORT:
     CYG_CACHE: C:/cygwin/var/cache/setup
     CYG_MIRROR: http://mirrors.kernel.org/sourceware/cygwin/
     DEP_MODE: lib-ext
     # This should be identical to the value in .travis.yml
+    OPAM_REPO: https://github.com/ocaml/opam-repository.git
     OPAM_REPO_SHA: 38e8f54c584fa3cfe779890f7a56fe88ee38be78
     OPAM_TEST_REPO_SHA: 38e8f54c584fa3cfe779890f7a56fe88ee38be78
   matrix:

appveyor_test.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
-opam init -y -a --compiler=ocaml.4.12.0 git+https://github.com/ocaml/opam-repository#$OPAM_TEST_REPO_SHA
+COLD_OCAML="$(sed -ne 's/URL_ocaml = .*ocaml-.*ocaml-\(.*\)\.tar\.gz/ocaml.\1/p' src_ext/Makefile)"
+# This is supposed to be able to select ocaml-system using the bootstrap compiler
+opam init -y -a --compiler=$COLD_OCAML git+$OPAM_REPO#$OPAM_TEST_REPO_SHA
 eval $(opam config env)
 opam install -y -v ocamlfind