glibc doesn't expose pread64 any more.

--- chmlib-0.39/src/chm_lib.c	2007-01-25 02:12:58.000000000 +0000
+++ chmlib-0.39/src/chm_lib.c	2025-07-03 17:11:04.490269369 +0100
@@ -724,7 +724,7 @@
 #else
 #ifdef CHM_USE_PREAD
 #ifdef CHM_USE_IO64
-    readLen = pread64(h->fd, buf, (long)len, os);
+    readLen = pread(h->fd, buf, (long)len, os);
 #else
     readLen = pread(h->fd, buf, (long)len, (unsigned int)os);
 #endif