$NetBSD: patch-bc,v 1.4 2018/08/06 12:55:38 snj Exp $

replacing explicit --export-dynamic by ${EXPORT_SYMBOLS_LDFLAGS}
for xlc

--- m4/libtool.m4.orig	2018-03-17 05:46:45.000000000 -0700
+++ m4/libtool.m4	2018-08-06 05:48:51.960497787 -0700
@@ -7032,7 +7032,7 @@ if test yes != "$_lt_caught_CXX_error"; 
 	  xl* | mpixl* | bgxl*)
 	    # IBM XL 8.0 on PPC, with GNU ld
 	    _LT_TAGVAR(hardcode_libdir_flag_spec, $1)='$wl-rpath $wl$libdir'
-	    _LT_TAGVAR(export_dynamic_flag_spec, $1)='$wl--export-dynamic'
+	    _LT_TAGVAR(export_dynamic_flag_spec, $1)='${EXPORT_SYMBOLS_LDFLAGS}'
 	    _LT_TAGVAR(archive_cmds, $1)='$CC -qmkshrobj $libobjs $deplibs $compiler_flags $wl-soname $wl$soname -o $lib'
 	    if test yes = "$supports_anon_versioning"; then
 	      _LT_TAGVAR(archive_expsym_cmds, $1)='echo "{ global:" > $output_objdir/$libname.ver~
