Fix:
The signature of the scandir function changed to include a const in OS X 10.8.
https://trac.macports.org/ticket/71181#comment:4
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271539

Patch derived from https://bugs.freebsd.org/bugzilla/attachment.cgi?id=242299&action=diff
--- src/osdep/unix/mh.c.orig	2022-04-17 00:12:02 UTC
+++ src/osdep/unix/mh.c
@@ -100,8 +100,8 @@ long mh_append (MAILSTREAM *stream,char *mailbox,appen
 	      long options);
 long mh_append (MAILSTREAM *stream,char *mailbox,append_t af,void *data);
 
-int mh_select (struct direct *name);
-int mh_numsort (const void *d1,const void *d2);
+int mh_select (const struct direct *name);
+int mh_numsort (const struct direct **d1,const struct direct **d2);
 char *mh_file (char *dst,char *name);
 long mh_canonicalize (char *pattern,char *ref,char *pat);
 void mh_setdate (char *file,MESSAGECACHE *elt);
@@ -1191,7 +1191,7 @@ long mh_append (MAILSTREAM *stream,char *mailbox,appen
  * Returns: T to use file name, NIL to skip it
  */
 
-int mh_select (struct direct *name)
+int mh_select (const struct direct *name)
 {
   char c;
   char *s = name->d_name;
@@ -1206,10 +1206,9 @@ int mh_select (struct direct *name)
  * Returns: negative if d1 < d2, 0 if d1 == d2, postive if d1 > d2
  */
 
-int mh_numsort (const void *d1,const void *d2)
+int mh_numsort (const struct direct **d1,const struct direct **d2)
 {
-  return atoi ((*(struct direct **) d1)->d_name) -
-    atoi ((*(struct direct **) d2)->d_name);
+  return atoi ((*d1)->d_name) - atoi ((*d2)->d_name);
 }
 
 
@ -0,0 +1,54 @@ 
--- src/osdep/unix/mix.c.orig	2022-04-17 00:12:02 UTC
+++ src/osdep/unix/mix.c
@@ -123,7 +123,7 @@ long mix_rename (MAILSTREAM *stream,char *old,char *ne
 long mix_create (MAILSTREAM *stream,char *mailbox);
 long mix_delete (MAILSTREAM *stream,char *mailbox);
 long mix_rename (MAILSTREAM *stream,char *old,char *newname);
-int mix_rselect (struct direct *name);
+int mix_rselect (const struct direct *name);
 MAILSTREAM *mix_open (MAILSTREAM *stream);
 void mix_close (MAILSTREAM *stream,long options);
 void mix_abort (MAILSTREAM *stream);
@@ -138,8 +138,8 @@ long mix_expunge (MAILSTREAM *stream,char *sequence,lo
 long mix_ping (MAILSTREAM *stream);
 void mix_check (MAILSTREAM *stream);
 long mix_expunge (MAILSTREAM *stream,char *sequence,long options);
-int mix_select (struct direct *name);
-int mix_msgfsort (const void *d1,const void *d2);
+int mix_select (const struct direct *name);
+int mix_msgfsort (const struct direct **d1,const struct direct **d2);
 long mix_addset (SEARCHSET **set,unsigned long start,unsigned long size);
 long mix_burp (MAILSTREAM *stream,MIXBURP *burp,unsigned long *reclaimed);
 long mix_burp_check (SEARCHSET *set,size_t size,char *file);
@@ -585,7 +585,7 @@ long mix_rename (MAILSTREAM *stream,char *old,char *ne
  * Returns: T if mix file name, NIL otherwise
  */
 
-int mix_rselect (struct direct *name)
+int mix_rselect (const struct direct *name)
 {
   return mix_dirfmttest (name->d_name);
 }
@@ -1150,7 +1150,7 @@ long mix_expunge (MAILSTREAM *stream,char *sequence,lo
  * ".mix" with no suffix was used by experimental versions
  */
 
-int mix_select (struct direct *name)
+int mix_select (const struct direct *name)
 {
   char c,*s;
 				/* make sure name has prefix */
@@ -1169,10 +1169,10 @@ int mix_select (struct direct *name)
  * Returns: -1 if d1 < d2, 0 if d1 == d2, 1 d1 > d2
  */
 
-int mix_msgfsort (const void *d1,const void *d2)
+int mix_msgfsort (const struct direct **d1,const struct direct **d2)
 {
-  char *n1 = (*(struct direct **) d1)->d_name + sizeof (MIXNAME) - 1;
-  char *n2 = (*(struct direct **) d2)->d_name + sizeof (MIXNAME) - 1;
+  char *n1 = (*d1)->d_name + sizeof (MIXNAME) - 1;
+  char *n2 = (*d2)->d_name + sizeof (MIXNAME) - 1;
   return compare_ulong (*n1 ? strtoul (n1,NIL,16) : 0,
 			*n2 ? strtoul (n2,NIL,16) : 0);
 }
--- src/osdep/unix/mx.c.orig	2022-04-17 00:12:02 UTC
+++ src/osdep/unix/mx.c
@@ -98,8 +98,8 @@ long mx_append_msg (MAILSTREAM *stream,char *flags,MES
 long mx_append_msg (MAILSTREAM *stream,char *flags,MESSAGECACHE *elt,
 		    STRING *st,SEARCHSET *set);
 
-int mx_select (struct direct *name);
-int mx_numsort (const void *d1,const void *d2);
+int mx_select (const struct direct *name);
+int mx_numsort (const struct direct **d1,const struct direct **d2);
 char *mx_file (char *dst,char *name);
 long mx_lockindex (MAILSTREAM *stream);
 void mx_unlockindex (MAILSTREAM *stream);
@@ -1110,7 +1110,7 @@ long mx_append_msg (MAILSTREAM *stream,char *flags,MES
  * Returns: T to use file name, NIL to skip it
  */
 
-int mx_select (struct direct *name)
+int mx_select (const struct direct *name)
 {
   char c;
   char *s = name->d_name;
@@ -1125,10 +1125,9 @@ int mx_select (struct direct *name)
  * Returns: negative if d1 < d2, 0 if d1 == d2, postive if d1 > d2
  */
 
-int mx_numsort (const void *d1,const void *d2)
+int mx_numsort (const struct direct **d1,const struct direct **d2)
 {
-  return atoi ((*(struct direct **) d1)->d_name) -
-    atoi ((*(struct direct **) d2)->d_name);
+  return atoi ((*d1)->d_name) - atoi ((*d2)->d_name);
 }
 
 
--- src/osdep/unix/news.c.orig	2022-04-17 00:12:02 UTC
+++ src/osdep/unix/news.c
@@ -76,8 +76,8 @@ MAILSTREAM *news_open (MAILSTREAM *stream);
 long news_delete (MAILSTREAM *stream,char *mailbox);
 long news_rename (MAILSTREAM *stream,char *old,char *newname);
 MAILSTREAM *news_open (MAILSTREAM *stream);
-int news_select (struct direct *name);
-int news_numsort (const void *d1,const void *d2);
+int news_select (const struct direct *name);
+int news_numsort (const struct direct **d1,const struct direct **d2);
 void news_close (MAILSTREAM *stream,long options);
 void news_fast (MAILSTREAM *stream,char *sequence,long flags);
 void news_flags (MAILSTREAM *stream,char *sequence,long flags);
@@ -402,7 +402,7 @@ MAILSTREAM *news_open (MAILSTREAM *stream)
  * Returns: T to use file name, NIL to skip it
  */
 
-int news_select (struct direct *name)
+int news_select (const struct direct *name)
 {
   char c;
   char *s = name->d_name;
@@ -417,10 +417,9 @@ int news_select (struct direct *name)
  * Returns: negative if d1 < d2, 0 if d1 == d2, postive if d1 > d2
  */
 
-int news_numsort (const void *d1,const void *d2)
+int news_numsort (const struct direct **d1,const struct direct **d2)
 {
-  return atoi ((*(struct direct **) d1)->d_name) -
-    atoi ((*(struct direct **) d2)->d_name);
+  return atoi ((*d1)->d_name) - atoi ((*d2)->d_name);
 }