mksquashfs: don't need to pass oldmask into pthread_sigmask(), it's not used later

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c
index aebbcb2..3653e2f 100644
--- a/squashfs-tools/mksquashfs.c
+++ b/squashfs-tools/mksquashfs.c
@@ -4005,7 +4005,7 @@
 	sigemptyset(&sigmask);
 	sigaddset(&sigmask, SIGQUIT);
 	sigaddset(&sigmask, SIGHUP);
-	if(pthread_sigmask(SIG_BLOCK, &sigmask, &old_mask) == -1)
+	if(pthread_sigmask(SIG_BLOCK, &sigmask, NULL) == -1)
 		BAD_ERROR("Failed to set signal mask in intialise_threads\n");
 
 	/*
@@ -5359,7 +5359,7 @@
 			SQUASHFS_INODE_BLK(sBlk.root_inode),
 			root_inode_offset =
 			SQUASHFS_INODE_OFFSET(sBlk.root_inode);
-		sigset_t sigmask, old_mask;
+		sigset_t sigmask;
 
 		if((bytes = read_filesystem(root_name, fd, &sBlk, &inode_table,
 				&data_cache, &directory_table,
@@ -5435,7 +5435,7 @@
 		sigaddset(&sigmask, SIGINT);
 		sigaddset(&sigmask, SIGTERM);
 		sigaddset(&sigmask, SIGUSR1);
-		if(pthread_sigmask(SIG_BLOCK, &sigmask, &old_mask) == -1)
+		if(pthread_sigmask(SIG_BLOCK, &sigmask, NULL) == -1)
 			BAD_ERROR("Failed to set signal mask\n");
 		write_destination(fd, SQUASHFS_START, 4, "\0\0\0\0");