[Bug c/100068] inconsistent handling of noreturn on nested function declarations

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100068

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
The latter: in f1() warn for the redeclaration of g1() in the nested scope. 
That's where GCC and other compilers differ.