[Bug driver/68794] an option for -fsanitize=<foo> is accepted even if the corresponding library is not available

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68794

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't we want to warn or error out if the library is not exits as someone
could implement their own runtime library which they install separately from
GCC.