cxx: don’t define stubs for __throw_* functions

cxx: don’t define stubs for __throw_* functions

If exception support is disabled in IDF, and libstdc++ tries to throw
an exception, it will call __cxa_allocate_exception which is replaced
with abort in IDF.

We have a dramatically size reduction of the RO-section in binary when using '__throw_'-stubs in GCC5
In the case of using GCC8, we are faced with 'multiple definition' errors when using '__throw_'-stubs.
Good that we don't have the size problem due to gcc8