swaylock: fix build with musl libc
swaylock: fix build with musl libc

Signed-off-by: Cameron Nemo <ebdc73d5d2e0ed5b9d45f08a109317f61170c5b8@gmail.com>

ascent12/sway,1ace/sway,ascent12/sway,1ace/sway,1ace/sway,SirCmpwn/sway,ascent12/sway