💚 fix appveyor build (#478)

* 💚🚧 remove -A x64

* ⏪ restore -A x64

* 💚 set cmake generator vs15 2017, not win64

Author: ToruNiina

conda.recipe/bld.bat

@@ -1,3 +1,4 @@
+set "CMAKE_GENERATOR=Visual Studio 15 2017"
 "%PYTHON%" setup.py install
 "%PYTHON%" setup.py test
 if errorlevel 1 exit 1