chore: update CI to github actions 2

.github/workflows/main.yml

@@ -1,7 +1,4 @@
 name: build
-
-# adapted from ocaml-containers and @fardale's hard work.
-
 on:
   push:
     branches:
@@ -9,69 +6,27 @@ on:
   pull_request:
     branches:
       - master
-
 jobs:
   run:
     name: Build
     strategy:
-      fail-fast: false
       matrix:
         os:
           - macos-latest
           - ubuntu-latest
           - windows-latest
-        ocaml:
+        ocaml-compiler:
-            - '4.08.1'
+          - 4.08.x
-            - '4.12.0'
+          - 4.12.x
-
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: haya14busa/action-cond@v1
+    - uses: actions/checkout@v2
-        id: path
+    - uses: ocaml/setup-ocaml@v2
       with:
-          cond: ${{ matrix.os == 'windows-latest' }}
+        ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          if_true: "D:\\cygwin\\home\\runneradmin\\.opam"
-          if_false: "~/.opam"
-
-      - name: Checkout code
-        uses: actions/checkout@main
-
-      - name: Cache opam
-        id: cache-opam
-        uses: actions/cache@v2
-        with:
-          path: ${{ steps.path.outputs.value }}
-          key: opam-${{ matrix.os }}-${{ matrix.ocaml }}
-
-      - name: Use OCaml ${{ matrix.ocaml }}
-        uses: avsm/setup-ocaml@v1
-        with:
-          ocaml-version: ${{ matrix.ocaml }}
-
-      - run: opam update -u
-        if: steps.cache-opam.outputs.cache-hit == 'true'
-
     - run: opam pin -n .
-
     - run: opam depext -yt linol linol-lwt
-
+    - run: opam install -t . --deps-only
-      - run: opam install -t linol linol-lwt --deps-only
-        if: matrix.os == 'ubuntu-latest'
-
-      - run: |
-          opam install -t linol --deps-only
-          opam install linol-lwt --deps-only  # no test deps
-        if: matrix.os != 'ubuntu-latest'
-
     - run: opam exec -- dune build
-
     - run: opam exec -- dune runtest
-        if: ${{ matrix.os == 'ubuntu-latest' }}
+      if: ${{ matrix.os == 'ubuntu-latest'}}
-
-      - run: opam exec -- dune runtest -j 1 -p linol # test only core on non-ubuntu platform
-        if: ${{ matrix.os != 'ubuntu-latest' }}
-
-      - name: Remove troublesome files for caching on windows
-        if: matrix.os == 'windows-latest'
-        run: |
-            if (Test-Path D:\\cygwin\\home\\runneradmin\\.opam\\ocaml-variants.${{ matrix.ocaml }}+mingw64c\\.opam-switch\\sources\\ocamlbuild.0.14.0\\examples\\){Remove-Item –path D:\\cygwin\\home\\runneradmin\\.opam\\ocaml-variants.${{ matrix.ocaml }}+mingw64c\\.opam-switch\\sources\\ocamlbuild.0.14.0\\examples\\ –recurse}