Patch for Emacs 29

[Po Lu]

Recent updates to Haiku are unable to build the Emacs 29 pretest:
cfsetspeed is present in termios.h, but is in /system/lib/libbsd.so (and
not the C library), leading to system headers conflicting with the
gnulib replacements.

The solution is to link Emacs with libbsd so that the system's version
can be found by gnulib.  Is this okay for Emacs 29?

diff --git a/configure.ac b/configure.ac
index fc846ce840b..6adc3dbd150 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2249,7 +2249,8 @@ AC_DEFUN
   ## Motif needs -lgen.
   unixware) LIBS_SYSTEM="-lsocket -lnsl -lelf -lgen" ;;
 
-  haiku) LIBS_SYSTEM="-lnetwork" ;;
+  # Recent versions of Haiku need -lbsd for cfsetspeed.
+  haiku) LIBS_SYSTEM="-lnetwork -lbsd" ;;
 esac
 
 AC_SUBST([LIBS_SYSTEM])