...that is curiously only reported when building with clang -std=gnu++17:

> sc/qa/unit/ucalc_condformat.cxx:185:80: error: redundant const_cast from 'ScConditionalFormat *' to 'const ScConditionalFormat *', result is implictly cast to 'const ScConditionalFormat *const' [loplugin:redundantcast]
>     CPPUNIT_ASSERT_EQUAL_MESSAGE("Wrong conditional format instance.", pCheck, const_cast<const ScConditionalFormat*>(pFormat));
>     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> workdir/UnpackedTarball/cppunit/include/cppunit/TestAssert.h:230:32: note: expanded from macro 'CPPUNIT_ASSERT_EQUAL_MESSAGE'
>                               (actual),                \
>                               ~^~~~~~~
> 1 error generated.
> make[1]: *** [solenv/gbuild/LinkTarget.mk:270: workdir/CxxObject/sc/qa/unit/ucalc_condformat.o] Error 1

Change-Id: If2e8577bad4ec7454d584eb59106734d47f876ad