Cherry pick trunk@13760 to remove boost::system
per https://marc.info/?l=openbsd-ports&m=177038373917003&w=2

Index: m4/ax_boost_system.m4
--- m4/ax_boost_system.m4.orig
+++ m4/ax_boost_system.m4
@@ -1,121 +0,0 @@
-# ===========================================================================
-#     https://www.gnu.org/software/autoconf-archive/ax_boost_system.html
-# ===========================================================================
-#
-# SYNOPSIS
-#
-#   AX_BOOST_SYSTEM
-#
-# DESCRIPTION
-#
-#   Test for System library from the Boost C++ libraries. The macro requires
-#   a preceding call to AX_BOOST_BASE. Further documentation is available at
-#   <http://randspringer.de/boost/index.html>.
-#
-#   This macro calls:
-#
-#     AC_SUBST(BOOST_SYSTEM_LIB)
-#
-#   And sets:
-#
-#     HAVE_BOOST_SYSTEM
-#
-# LICENSE
-#
-#   Copyright (c) 2008 Thomas Porschberg <thomas@randspringer.de>
-#   Copyright (c) 2008 Michael Tindal
-#   Copyright (c) 2008 Daniel Casimiro <dan.casimiro@gmail.com>
-#
-#   Copying and distribution of this file, with or without modification, are
-#   permitted in any medium without royalty provided the copyright notice
-#   and this notice are preserved. This file is offered as-is, without any
-#   warranty.
-
-#serial 19
-
-AC_DEFUN([AX_BOOST_SYSTEM],
-[
-	AC_ARG_WITH([boost-system],
-	AS_HELP_STRING([--with-boost-system@<:@=special-lib@:>@],
-                   [use the System library from boost - it is possible to specify a certain library for the linker
-                        e.g. --with-boost-system=boost_system-gcc-mt ]),
-        [
-        if test "$withval" = "no"; then
-			want_boost="no"
-        elif test "$withval" = "yes"; then
-            want_boost="yes"
-            ax_boost_user_system_lib=""
-        else
-		    want_boost="yes"
-		ax_boost_user_system_lib="$withval"
-		fi
-        ],
-        [want_boost="yes"]
-	)
-
-	if test "x$want_boost" = "xyes"; then
-        AC_REQUIRE([AC_PROG_CC])
-        AC_REQUIRE([AC_CANONICAL_BUILD])
-		CPPFLAGS_SAVED="$CPPFLAGS"
-		CPPFLAGS="$CPPFLAGS $BOOST_CPPFLAGS"
-		export CPPFLAGS
-
-		LDFLAGS_SAVED="$LDFLAGS"
-		LDFLAGS="$LDFLAGS $BOOST_LDFLAGS"
-		export LDFLAGS
-
-        AC_CACHE_CHECK(whether the Boost::System library is available,
-					   ax_cv_boost_system,
-        [AC_LANG_PUSH([C++])
-			 CXXFLAGS_SAVE=$CXXFLAGS
-			 CXXFLAGS=
-
-			 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[@%:@include <boost/system/error_code.hpp>]],
-				    [[boost::system::error_category *a = 0;]])],
-                   ax_cv_boost_system=yes, ax_cv_boost_system=no)
-			 CXXFLAGS=$CXXFLAGS_SAVE
-             AC_LANG_POP([C++])
-		])
-		if test "x$ax_cv_boost_system" = "xyes"; then
-			AC_SUBST(BOOST_CPPFLAGS)
-
-			AC_DEFINE(HAVE_BOOST_SYSTEM,,[define if the Boost::System library is available])
-            BOOSTLIBDIR=`echo $BOOST_LDFLAGS | sed -e 's/@<:@^\/@:>@*//'`
-
-			LDFLAGS_SAVE=$LDFLAGS
-            if test "x$ax_boost_user_system_lib" = "x"; then
-                for libextension in `ls -r $BOOSTLIBDIR/libboost_system* 2>/dev/null | sed 's,.*/lib,,' | sed 's,\..*,,'` ; do
-                     ax_lib=${libextension}
-				    AC_CHECK_LIB($ax_lib, exit,
-                                 [BOOST_SYSTEM_LIB="-l$ax_lib"; AC_SUBST(BOOST_SYSTEM_LIB) link_system="yes"; break],
-                                 [link_system="no"])
-				done
-                if test "x$link_system" != "xyes"; then
-                for libextension in `ls -r $BOOSTLIBDIR/boost_system* 2>/dev/null | sed 's,.*/,,' | sed -e 's,\..*,,'` ; do
-                     ax_lib=${libextension}
-				    AC_CHECK_LIB($ax_lib, exit,
-                                 [BOOST_SYSTEM_LIB="-l$ax_lib"; AC_SUBST(BOOST_SYSTEM_LIB) link_system="yes"; break],
-                                 [link_system="no"])
-				done
-                fi
-
-            else
-               for ax_lib in $ax_boost_user_system_lib boost_system-$ax_boost_user_system_lib; do
-				      AC_CHECK_LIB($ax_lib, exit,
-                                   [BOOST_SYSTEM_LIB="-l$ax_lib"; AC_SUBST(BOOST_SYSTEM_LIB) link_system="yes"; break],
-                                   [link_system="no"])
-                  done
-
-            fi
-            if test "x$ax_lib" = "x"; then
-                AC_MSG_ERROR(Could not find a version of the library!)
-            fi
-			if test "x$link_system" = "xno"; then
-				AC_MSG_ERROR(Could not link against $ax_lib !)
-			fi
-		fi
-
-		CPPFLAGS="$CPPFLAGS_SAVED"
-	LDFLAGS="$LDFLAGS_SAVED"
-	fi
-])
