cmake HAVE_STD_UNCAUGHT_EXCEPTIONS examples

CTSRD-CHERI/cheribsd contrib/subrepo-cheri-libcxxrt/test/CMakeLists.txt :11 

check_cxx_symbol_exists(std::uncaught_exceptions stdexcept HAVE_STD_UNCAUGHT_EXCEPTIONS)

CTSRD-CHERI/cheribsd contrib/subrepo-cheri-libcxxrt/test/CMakeLists.txt :13 

add_definitions(-DHAVE_STD_UNCAUGHT_EXCEPTIONS)