Try to fail build step without build.cmd

Author: abelbraaksma

.github/workflows/build.yaml

@@ -17,4 +17,4 @@ jobs:
         uses: actions/setup-dotnet@v3
       # build it, test it, pack it
       - name: Run dotnet build (release)
-        run: ./build.cmd
+        run: dotnet build ./src/FSharp.Control.TaskSeq.sln -c release