[CI] [Windows] Attempt to fix Windows CI (#1962)

* Use bash more explicitly

Work around
```
opam exec -- etc/ci/github-actions-make.sh -j2 deps
Fatal error: exception C:\hostedtoolcache\windows\opam\2.2.1\x86_64\opam.exe: "create_process" failed on etc/ci/github-actions-make.sh: Exec format error
```

* Install conf-gcc for `cc -O0 special/stackloop.c -o special/stackloop`

* CC=gcc

* setup OCaml fails with CC=gcc

* Update coq-windows.yml

Author: JasonGross

.github/workflows/coq-windows.yml

@@ -47,30 +47,30 @@ jobs:
     - run: opam pin add ocamlfind 'git+https://github.com/ocaml/ocamlfind.git#master'
     - run: opam pin add --kind=version coq ${{ env.COQ_VERSION }}
     - run: opam install js_of_ocaml
-    - run: opam install conf-time
+    - run: opam install conf-time conf-gcc
     - name: Work around https://github.com/actions/checkout/issues/766
       run: opam exec -- bash -l -c 'git config --global --add safe.directory "*"'
     - name: echo build params
       run: .\etc\ci\describe-system-config-win.ps1
     - name: deps
-      run: opam exec -- etc/ci/github-actions-make.sh -j${{ env.NJOBS }} deps
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j${{ env.NJOBS }} CC=gcc deps
     - name: standalone-ocaml
-      run: opam exec -- etc/ci/github-actions-make.sh -j${{ env.NJOBS }} standalone-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j${{ env.NJOBS }} standalone-ocaml
     - name: install-standalone-unified-ocaml
-      run: opam exec -- etc/ci/github-actions-make.sh install-standalone-unified-ocaml BINDIR=dist
+      run: opam exec -- bash etc/ci/github-actions-make.sh install-standalone-unified-ocaml BINDIR=dist
 
     - name: coq
-      run: opam exec -- etc/ci/github-actions-make.sh -j1 coq
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j1 coq
     - name: all-except-generated-and-js-of-ocaml
-      run: opam exec -- etc/ci/github-actions-make.sh -j1 all-except-generated-and-js-of-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j1 all-except-generated-and-js-of-ocaml
     - name: standalone-js-of-ocaml
-      run: opam exec -- etc/ci/github-actions-make.sh -j1 standalone-js-of-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j1 standalone-js-of-ocaml
     - name: install-standalone-js-of-ocaml
-      run: opam exec -- etc/ci/github-actions-make.sh install-standalone-js-of-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh install-standalone-js-of-ocaml
     - name: c-files lite-generated-files
-      run: opam exec -- etc/ci/github-actions-make.sh -j${{ env.NJOBS }} c-files lite-generated-files
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j${{ env.NJOBS }} c-files lite-generated-files
     - name: only-test-amd64-files-lite
-      run: opam exec -- etc/ci/github-actions-make.sh -j${{ env.NJOBS }} only-test-amd64-files-lite SLOWEST_FIRST=1
+      run: opam exec -- bash etc/ci/github-actions-make.sh -j${{ env.NJOBS }} only-test-amd64-files-lite SLOWEST_FIRST=1
     - name: upload OCaml files
       uses: actions/upload-artifact@v4
       with:
@@ -92,11 +92,11 @@ jobs:
         name: standalone-html-windows
         path: fiat-html
     - name: install
-      run: opam exec -- etc/ci/github-actions-make.sh EXTERNAL_DEPENDENCIES=1 SKIP_COQSCRIPTS_INCLUDE=1 install install-standalone-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh EXTERNAL_DEPENDENCIES=1 SKIP_COQSCRIPTS_INCLUDE=1 install install-standalone-ocaml
     - name: install-without-bedrock2
-      run: opam exec -- etc/ci/github-actions-make.sh EXTERNAL_DEPENDENCIES=1 SKIP_BEDROCK2=1 install-without-bedrock2 install-standalone-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh EXTERNAL_DEPENDENCIES=1 SKIP_BEDROCK2=1 install-without-bedrock2 install-standalone-ocaml
     - name: install-dev
-      run: opam exec -- etc/ci/github-actions-make.sh EXTERNAL_REWRITER=1 EXTERNAL_COQPRIME=1 install install-standalone-ocaml
+      run: opam exec -- bash etc/ci/github-actions-make.sh EXTERNAL_REWRITER=1 EXTERNAL_COQPRIME=1 install install-standalone-ocaml
     - name: display timing info
       run: type time-of-build-pretty.log
       shell: cmd