Speed up AppVeyor build times

* Examples are no longer built for all images
* Coverage is no longer collected from every build
* The number of configurations is reduced

misc/appveyorTestRunScript.bat

@@ -1,8 +1,12 @@
 cd Build
 if "%CONFIGURATION%"=="Debug" (
-  ctest -j 2 -C %CONFIGURATION% -D ExperimentalMemCheck
-  python ..\misc\appveyorMergeCoverageScript.py
-  codecov --root .. --no-color --disable gcov -f cobertura.xml -t %CODECOV_TOKEN%
+  if "%coverage%"=="1" (
+    ctest -j 2 -C %CONFIGURATION% -D ExperimentalMemCheck
+    python ..\misc\appveyorMergeCoverageScript.py
+    codecov --root .. --no-color --disable gcov -f cobertura.xml -t %CODECOV_TOKEN%
+  ) else (
+    ctest -j 2 -C %CONFIGURATION%
+  )
 )
 if "%CONFIGURATION%"=="Release" (
   ctest -j 2 -C %CONFIGURATION%