Add compiler warnings suppressions option for ctest_build
https://cmake.org/cmake/help/latest/manual/cmake-variables.7.html#variables-for-ctest includes things like CTEST_CUSTOM_MEMCHECK_IGNORE to filter warnings/errors, but I can't see any to filter-out compiler warnings.
It would be nice to have one. I would suggest using Buildbot's format (https://docs.buildbot.net/current/manual/configuration/buildsteps.html#compile) for it.