[ci] build examples on appveyor

Author: fabiencastan

appveyor.yml

@@ -20,7 +20,7 @@ install:
 before_build:
     - md build
     - cd build
-    - cmake -G "Visual Studio 14 2015" -A x64 -T v140,host=x64 -DPopSift_BUILD_EXAMPLES:BOOL=OFF -DCMAKE_BUILD_TYPE=%configuration% -DCMAKE_TOOLCHAIN_FILE=c:/tools/vcpkg/scripts/buildsystems/vcpkg.cmake ..
+    - cmake -G "Visual Studio 14 2015" -A x64 -T v140,host=x64 -DPopSift_BUILD_EXAMPLES:BOOL=ON -DCMAKE_BUILD_TYPE=%configuration% -DCMAKE_TOOLCHAIN_FILE=c:/tools/vcpkg/scripts/buildsystems/vcpkg.cmake ..
     - ls -l
 
 build: