macOS has sys/sbuf.h but uses a different API, so rather rely on compat implementation.

--- Makefile	2026-07-06 07:58:22.000000000 +0800
+++ Makefile	2026-07-17 18:08:47.000000000 +0800
@@ -54,13 +54,9 @@
 # Darwin and FreeBSD have these helpful functions.
 # Provide compat implementations, if not.
 
-.if $(UNAME) == "Darwin" || $(UNAME) == "FreeBSD"
-LDADD	  += -lsbuf
-CFLAGS	  += -DHAVE_SBUF
-.endif
 .if $(UNAME) == "FreeBSD"
-LDADD	  += -lutil
-CFLAGS	  += -DHAVE_HUMANIZE_NUMBER
+LDADD	  += -lsbuf -lutil
+CFLAGS	  += -DHAVE_HUMANIZE_NUMBER -DHAVE_SBUF
 .endif
 
 CFLAGS	  += $(CFLAGS_FTS) $(CFLAGS_Z)

These are not really required given above, but still, better not to include a header that does not exist.

--- log.c	2026-07-06 07:58:22.000000000 +0800
+++ log.c	2026-07-17 17:56:37.000000000 +0800
@@ -20,11 +20,7 @@
 #include COMPAT_ENDIAN_H
 
 #if HAVE_SBUF
-# if __APPLE__
-#  include <usbuf.h>
-# else
-#  include <sys/sbuf.h>
-# endif
+# include <sys/sbuf.h>
 #else
 # include "compat_sbuf.h"
 #endif

--- regress/cunit/print_7_or_8_bit.c	2026-07-06 07:58:22.000000000 +0800
+++ regress/cunit/print_7_or_8_bit.c	2026-07-17 18:11:16.000000000 +0800
@@ -6,11 +6,7 @@
 #include <sys/types.h>
 
 #if HAVE_SBUF
-# if __APPLE__
-#  include <usbuf.h>
-# else
-#  include <sys/sbuf.h>
-# endif
+# include <sys/sbuf.h>
 #else
 # include "../../compat_sbuf.h"
 #endif