appveyor: add verbose output to see warnings

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Author: neheb

appveyor.yml

@@ -19,7 +19,7 @@ build_script:
   # - ctest -D Experimental(Start|Update|Configure|Build|Test|Coverage|MemCheck|Submit)
   # NOTE: Testing on window is not yet finished:
   # - ctest -C Release -D ExperimentalStart -D ExperimentalConfigure -D ExperimentalBuild -D ExperimentalTest -D ExperimentalSubmit
-  - ctest -C Release -D ExperimentalStart -D ExperimentalConfigure -D ExperimentalBuild -D ExperimentalSubmit
+  - ctest -C Release -D ExperimentalStart -D ExperimentalConfigure -D ExperimentalBuild -D ExperimentalSubmit -V
   # Final step is to verify that installation succeeds
   - cmake --build . --config Release --target install