I noticed this yesterday when trying to package the dlang onedrive client in Gentoo with GDC 13.2 and it failed since it requires this.
It appears to have been removed when gdc became self-hosting in gcc during the gcc-12 release cycle.
There when it was present: https://github.com/gcc-mirror/gcc/tree/releases/gcc-11.2.0/libphobos/src/etc/c
Gone now: https://github.com/gcc-mirror/gcc/tree/releases/gcc-13.2.0/libphobos/src/etc/c
Still in dmd: https://github.com/dlang/phobos/blob/master/etc/c/sqlite3.d
I've asked in the #d IRC channel on Libera, and their guess was it was omitted by mistake so I'm writing in to verify: Would you know whether it's a bug and will return or otherwise why it got dropped? Thanks!