seatd-launch -- privilege escalation with SUID

Kenny Levinsen reports:

seatd-launch used execlp, which reads the PATH environment variable to
search for the requested executable, to execute seatd. This meant that
the caller could freely control what executable was loaded by adding a
user-writable directory to PATH.
If seatd-launch had the SUID bit set, this could be used by a
malicious user with the ability to execute seatd-launch to mount a
privilege escalation attack to the owner of seatd-launch, which is
likely root.