5.6.1-2 is not an attempted fix, it's just some tweaks to Arch's own build script to improve reproducibility. Arch's build script ultimately delegates to the compromised build script unfortunately, but it also appears the payload itself is specifically targeting deb/RPM based distros, so a narrow miss for Arch here.

(EDIT: as others have pointed out, part of the exploit is in the artifact from libxz, which Arch is now avoiding by switching to building from a git checkout)