This removes result for check on cups,
it is required as other checkers already print yes/no during the
test, even if it seems like the command is now "unresulted".

Just disable the warning then instead to avoid ugly casts.

So override the T_CXXFLAGS for the yacc-generated source file to use
gb_LinkTarget_EXCEPTIONFLAGS. Seems to work.

It pulls external library and does not just switch some internal
feature.

Add proper bool logic to the conditional because by default
we consider it requested unless proven otherwise.
Sort out internal/external switch to also support system-libs switch.