Downgrade setup-ocaml to 3.1.5. (#11906)

* Downgrade setup-ocaml to 3.1.5.

* Set $PSNativeCommandUseErrorActionPreference = $true in the install OCaml libraries step.
This ensures that the step fails if any opam commands fail.

.github/workflows/main.yml

@@ -46,7 +46,7 @@ jobs:
         run: neko -version 2>&1
 
       - name: Setup ocaml
-        uses: ocaml/setup-ocaml@v3
+        uses: ocaml/setup-ocaml@v3.1.5
         with:
           ocaml-compiler: 4
           opam-local-packages: |
@@ -65,6 +65,9 @@ jobs:
         shell: pwsh
         run: |
           Set-PSDebug -Trace 1
+          # stop after any command returns an error
+          $PSNativeCommandUseErrorActionPreference = $true
+          $ErrorActionPreference = 'Stop'
           # see: https://github.com/aantron/luv/issues/162
           $env:PATH="${env:CYG_ROOT}\bin;${env:CYG_ROOT}\usr\x86_64-w64-mingw32\bin;${env:PATH}"
           opam install haxe --deps-only

extra/github-actions/install-ocaml-libs-windows.yml

@@ -2,6 +2,9 @@
   shell: pwsh
   run: |
     Set-PSDebug -Trace 1
+    # stop after any command returns an error
+    $PSNativeCommandUseErrorActionPreference = $true
+    $ErrorActionPreference = 'Stop'
     # see: https://github.com/aantron/luv/issues/162
     $env:PATH="${env:CYG_ROOT}\bin;${env:CYG_ROOT}\usr\x86_64-w64-mingw32\bin;${env:PATH}"
     opam install haxe --deps-only

extra/github-actions/install-ocaml-windows.yml

@@ -1,5 +1,5 @@
 - name: Setup ocaml
-  uses: ocaml/setup-ocaml@v3
+  uses: ocaml/setup-ocaml@v3.1.5
   with:
     ocaml-compiler: 4
     opam-local-packages: |