[Bug bootstrap/116951] Use -D_GLIBCXX_ASSERTIONS for --enable-checking=yes

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116951

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Not "stl" though please.

STL != the C++ standard library