tests: A new target check to build+run targets

The CMake test target does not build tests it just runs them - the
rationale for this is that CTest is used to run tests, and the ALL
target to build them.

Added a new target **check** to build and run the tests.

test/CMakeLists.txt

@@ -1,10 +1,12 @@
 
 include_directories(${CMAKE_SOURCE_DIR}/src)
 
+add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND})
 function(add_xtest SOURCE_NAME)
 	add_executable(${SOURCE_NAME} ${SOURCE_NAME}.cpp)
 	target_link_libraries(${SOURCE_NAME} Qt5::Network Qt5::Test ${MSGPACK_LIBRARIES} neovim-qt)
 	add_test(NAME ${SOURCE_NAME} COMMAND ${SOURCE_NAME})
+	add_dependencies(check ${SOURCE_NAME})
 endfunction()
 
 add_xtest(tst_neovimobject)