building.md: fix clang/clang++ arg
building.md: fix clang/clang++ arg

Whilst most versions of clang autodetect whether the code is C or C++ it seems
more recent versions do not do this correctly. Fix the doc to make sure this
works all the time

Signed-off-by: Brendan Le Foll <3e0e8c4069934e8b47d99704927a85c66c0ceb33@intel.com>
Signed-off-by: Sarah Knepper <aa6f32c7068de0436ab460eb7d52c137f945f426@intel.com>

sasmita/upm,rafaneri/upm,kissbac/upm,noahchense/upm,andreivasiliu2211/upm,yoyojacky/upm,skiselev/upm,srware/upm,srware/upm,spitfire88/upm,izard/upm,MakerCollider/upm,g-vidal/upm,fieldhawker/upm,GSmurf/upm,stefan-andritoiu/upm,0xD34D/upm,spitfire88/upm,ShawnHymel/upm,tylergibson/upm,jontrulson/upm,tripzero/upm,fieldhawker/upm,afmckinney/upm,MakerCollider/upm,andreivasiliu2211/upm,noahchense/upm,tylergibson/upm,andreivasiliu2211/upm,srware/upm,GSmurf/upm,whbruce/upm,srware/upm,g-vidal/upm,ShawnHymel/upm,malikabhi05/upm,Propanu/upm,nitirohilla/upm,fieldhawker/upm,Vaghesh/upm,jontrulson/upm,Jon-ICS/upm,nitirohilla/upm,arfoll/upm,tylergibson/upm,malikabhi05/upm,afmckinney/upm,g-vidal/upm,intel-iot-devkit/upm,mircea/upm,skiselev/upm,rafaneri/upm,tylergibson/upm,Propanu/upm,MakerCollider/upm,nitirohilla/upm,tripzero/upm,afmckinney/upm,intel-iot-devkit/upm,Vaghesh/upm,ShawnHymel/upm,pylbert/upm,Propanu/upm,g-vidal/upm,whbruce/upm,afmckinney/upm,skiselev/upm,whbruce/upm,yoyojacky/upm,0xD34D/upm,whbruce/upm,tylergibson/upm,intel-iot-devkit/upm,Propanu/upm,mircea/upm,skiselev/upm,Propanu/upm,yoyojacky/upm,rafaneri/upm,malikabhi05/upm,intel-iot-devkit/upm,GSmurf/upm,0xD34D/upm,malikabhi05/upm,pylbert/upm,pylbert/upm,malikabhi05/upm,jontrulson/upm,sasmita/upm,MakerCollider/upm,izard/upm,kissbac/upm,spitfire88/upm,arfoll/upm,spitfire88/upm,GSmurf/upm,arfoll/upm,rafaneri/upm,srware/upm,stefan-andritoiu/upm,tripzero/upm,g-vidal/upm,yoyojacky/upm,noahchense/upm,nitirohilla/upm,noahchense/upm,arfoll/upm,stefan-andritoiu/upm,pylbert/upm,andreivasiliu2211/upm,sasmita/upm,Jon-ICS/upm,stefan-andritoiu/upm,sasmita/upm,sasmita/upm,MakerCollider/upm,skiselev/upm,Jon-ICS/upm,stefan-andritoiu/upm,g-vidal/upm,stefan-andritoiu/upm,0xD34D/upm,jontrulson/upm,pylbert/upm,mircea/upm,kissbac/upm,izard/upm,whbruce/upm,arfoll/upm,Vaghesh/upm,kissbac/upm,spitfire88/upm,skiselev/upm,Jon-ICS/upm,jontrulson/upm,Jon-ICS/upm,intel-iot-devkit/upm,fieldhawker/upm,malikabhi05/upm,Propanu/upm,pylbert/upm,kissbac/upm,rafaneri/upm,ShawnHymel/upm,mircea/upm,intel-iot-devkit/upm,afmckinney/upm,nitirohilla/upm,tripzero/upm,Vaghesh/upm,tripzero/upm,yoyojacky/upm,mircea/upm,ShawnHymel/upm,andreivasiliu2211/upm