AFAIU the extra line in the output (libgcc_s.so.1 must be installed for pthread_cancel to work) appears when mksquashfs is invoked as squashfs-tools is missing a dependency on libgc-s1 (previously libgcc1).
AFAIU the extra line in the output (libgcc_s.so.1 must be installed for pthread_cancel to work) appears when mksquashfs is invoked as squashfs-tools is missing a dependency on libgc-s1 (previously libgcc1).