Install bison and flex on the windows cmake build from cyg-get

Because the chocolatey package for flex and bison is currently broken,
due to a dead link.

Author: thomasspriggs

buildspec-windows-cmake.yml

@@ -9,7 +9,8 @@ phases:
   install:
     commands:
       - choco install -y --no-progress cmake --installargs 'ADD_CMAKE_TO_PATH=System'
-      - choco install -y --no-progress winflexbison3 ninja
+      - cyg-get bison flex
+      - choco install -y --no-progress ninja
       - nuget install clcache -OutputDirectory "c:\tools" -ExcludeVersion -Version 4.1.0
 
   build: