See https://www.openwall.com/lists/musl/2013/01/23/6
--- a/include/reiserfs_lib.h
+++ b/include/reiserfs_lib.h
@@ -3,6 +3,10 @@
  *  reiserfsprogs/README
  */
 
+#if !defined(__GLIBC__)
+#define loff_t off_t
+#endif
+
 #ifndef REISERFSPROGS_LIB_H
 #define REISERFSPROGS_LIB_H