[Bug libstdc++/79162] [7/8 Regression] [C++17] ambiguity in string assignment due to string_view overload

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79162

--- Comment #18 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk so far.