Use Visual Studio and CMake in Windows CI builds

With CMake we can actually build natively on Windows/Visual Studio, there should
not be any need for Cygwin.

Author: tautschnig

buildspec-windows.yml

@@ -4,11 +4,16 @@ phases:
   install:
     commands:
       - choco install cyg-get -y --no-progress
+      - choco install cmake --installargs 'ADD_CMAKE_TO_PATH=System'
       - cyg-get bash patch bison flex make wget perl jq
       - nuget install clcache -OutputDirectory "c:\tools" -ExcludeVersion -Version 4.1.0
 
   build:
     commands:
+      - |
+        cmake -Bbuild -H. -GNMake
+        cmake --build build
+
       - |
         $env:Path = "C:\tools\cygwin\bin;$env:Path"
         bash -c "make -C src minisat2-download DOWNLOADER=wget"