[Bug other/102664] contrib/gcc-git-customization.sh uses echo -n, which isn't portable

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102664

--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Using "${r}" instead of ${r:-no} would be simpler too, but that can be done
separately.