Reduce AppVeyor build verbosity by passing extra args to sub-CMake

appveyor.yml

@@ -58,9 +58,11 @@ install:
   # the current PATH.
   - echo cmake -G "%generator_name%" -DDEBUG=1
     -DBOXBACKUP_VERSION=%compiled_version%
+    -DSUB_CMAKE_EXTRA_ARGS="-- /verbosity:minimal"
     %APPVEYOR_BUILD_FOLDER%\infrastructure\cmake\windows
   - cmake -G "%generator_name%" -DDEBUG=1
     -DBOXBACKUP_VERSION=%compiled_version%
+    -DSUB_CMAKE_EXTRA_ARGS="-- /verbosity:minimal"
     %APPVEYOR_BUILD_FOLDER%\infrastructure\cmake\windows
 
   # Leave the current directory in the correct place to find the solution file using its relative path above.

infrastructure/cmake/windows/CMakeLists.txt

@@ -35,7 +35,7 @@ ExternalProject_Add(zlib
 	URL "http://zlib.net/zlib-${ZLIB_VERSION}.tar.gz"
 	URL_HASH ${ZLIB_HASH}
 	DOWNLOAD_NO_PROGRESS 1
-	CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${install_dir}
+	CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${install_dir} ${SUB_CMAKE_EXTRA_ARGS}
 	# We need to build both versions, debug and release, because cmake requires both to be
 	# present to generate its multi-configuration project files for Visual Studio/MSBuild.
 	INSTALL_COMMAND ${CMAKE_COMMAND} --build <BINARY_DIR> --target install --config Debug
@@ -86,7 +86,7 @@ ExternalProject_Add(pcre
 	SVN_REPOSITORY svn://vcs.exim.org/pcre/code/trunk
 	SVN_REVISION -r 1677
 	DOWNLOAD_NO_PROGRESS 1
-	CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${install_dir}
+	CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${install_dir} ${SUB_CMAKE_EXTRA_ARGS}
 	-DPCRE_SUPPORT_LIBREADLINE=OFF
 	-DPCRE_SUPPORT_LIBBZ2=OFF
 	# We need to build both versions, debug and release, because cmake requires both to be
@@ -122,5 +122,6 @@ ExternalProject_Add(boxbackup
 		-DAPPVEYOR_MODE=1
 		-DDEBUG=${DEBUG}
 		${boxbackup_cmake_args}
+		${SUB_CMAKE_EXTRA_ARGS}
 	STEP_TARGETS configure build install
 )