pie.md

GCC

• Alpine Linux
• Arch Linux
• Debian, Ubuntu (on for most arches)
• Fedora does it via spec files globally, not via toolchain
• Gentoo (on for almost every arch by default, obviously in Gentoo you can toggle it easily if you want)
• openSUSE has an interesting gcc-pie package instead which provides a spec file
• Void Linux

LLVM

• Arch Linux has patched it in (on by default) for Clang for a while
• Gentoo wanted to use it sooner but was waiting for an upstream acceptable patch to avoid rebasing, since 14+ is on by default
• Chimera Linux and any LLVM based musl distros will be using it as it is forced on for musl in LLVM anyway

Most distributions do not use an LLVM-based toolchain by default because this mostly (until very very recently) required using non-glibc. Hence there has been less importance or regard for what LLVM's default was until recently because it was not used as a system compiler.