https://github.com/plougher/squashfs-tools/pull/69
with the lutimes(3) changes removed and prefer _SC_NPROCESSORS_ONLN

Index: squashfs-tools/unsquashfs.c
--- squashfs-tools/unsquashfs.c.orig
+++ squashfs-tools/unsquashfs.c
@@ -32,8 +32,13 @@
 #include "stdarg.h"
 #include "fnmatch_compat.h"
 
+#ifndef _SC_NPROCESSORS_ONLN
+#include <sys/sysctl.h>
+#endif
+#ifdef linux
 #include <sys/sysinfo.h>
 #include <sys/sysmacros.h>
+#endif
 #include <sys/types.h>
 #include <sys/time.h>
 #include <sys/resource.h>
@@ -2245,6 +2250,7 @@ void initialise_threads(int fragment_buffer_size, int 
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
+	sigaddset(&sigmask, SIGALRM);
 	if(pthread_sigmask(SIG_BLOCK, &sigmask, NULL) != 0)
 		EXIT_UNSQUASH("Failed to set signal mask in initialise_threads"
 			"\n");
@@ -2261,7 +2267,9 @@ void initialise_threads(int fragment_buffer_size, int 
 			"\n");
 
 	if(processors == -1) {
-#ifndef linux
+#ifdef _SC_NPROCESSORS_ONLN
+		processors = sysconf(_SC_NPROCESSORS_ONLN);
+#else
 		int mib[2];
 		size_t len = sizeof(processors);
 
@@ -2277,8 +2285,6 @@ void initialise_threads(int fragment_buffer_size, int 
 				"Defaulting to 1\n");
 			processors = 1;
 		}
-#else
-		processors = sysconf(_SC_NPROCESSORS_ONLN);
 #endif
 	}