add a no-thunks CI build variant

.github/workflows/cabal.project.no-thunks.local

@@ -0,0 +1,8 @@
+package cardano-crypto-praos
+  flags: -external-libsodium-vrf
+
+package strict-checked-vars
+  flags: +checktvarinvariants +checkmvarinvariants
+
+program-options
+  ghc-options: -Werror

.github/workflows/ci.yml

@@ -12,6 +12,8 @@ on:
   push:
     branches:
       - main
+  schedule:
+    - cron: "0 0 * * *"
 
 jobs:
   build-test-bench-haddocks:
@@ -23,6 +25,10 @@ jobs:
          ghc: ["8.10.7", "9.6.4", "9.8.1"]
          cabal: ["3.10.2.1"]
          os: [ubuntu-latest]
+         variant: [default, no-thunks]
+         exclude:
+          variant:
+            ${{ github.event_name == 'schedule' ? 'no-thunks' : 'default' }}
     env:
       # Modify this value to "invalidate" the Cabal cache.
       CABAL_CACHE_VERSION: "2024-01-29"
@@ -44,7 +50,7 @@ jobs:
 
     - name: Configure Cabal
       run: |
-        cp .github/workflows/cabal.project.local .
+        cp .github/workflows/cabal.project.${{ matrix.variant}}.local ./cabal.project.local
 
     - name: Update Cabal (Hackage and CHaP)
       run: |
@@ -172,7 +178,8 @@ jobs:
       if: |
         github.event_name == 'push'
         && github.ref == 'refs/heads/main'
-        && matrix.ghc=='9.6.4'
+        && matrix.ghc == '9.6.4'
+        && matrix.variant == 'default'
       run: |
         # need for latex, dvisvgm and standalone
         sudo apt install texlive-latex-extra texlive-latex-base
@@ -188,6 +195,7 @@ jobs:
         github.event_name == 'push'
         && github.ref == 'refs/heads/main'
         && matrix.ghc=='9.6.4'
+        && matrix.variant == 'default'
       uses: actions/upload-artifact@v4
       with:
         name: haddocks