--- /dev/null
+++ b/build-aux/symbol_uscore.m4
@@ -0,0 +1,50 @@
+# ltdl.m4 - Configure ltdl for the target system. -*-Autoconf-*-
+#
+#   Copyright (C) 1999-2008, 2011-2015 Free Software Foundation, Inc.
+#   Written by Thomas Tanner, 1999
+#
+# This file is free software; the Free Software Foundation gives
+# unlimited permission to copy and/or distribute it, with or without
+# modifications, as long as this notice is preserved.
+
+# This macro has been copied from /usr/share/aclocal/ltdl.m4,
+# part of libltdl-dev 2.4.6-15.
+
+# LT_SYS_SYMBOL_USCORE
+# --------------------
+# does the compiler prefix global symbols with an underscore?
+AC_DEFUN([LT_SYS_SYMBOL_USCORE],
+[m4_require([_LT_CMD_GLOBAL_SYMBOLS])dnl
+AC_CACHE_CHECK([for _ prefix in compiled symbols],
+  [lt_cv_sys_symbol_underscore],
+  [lt_cv_sys_symbol_underscore=no
+  cat > conftest.$ac_ext <<_LT_EOF
+void nm_test_func(){}
+int main(){nm_test_func;return 0;}
+_LT_EOF
+  if AC_TRY_EVAL(ac_compile); then
+    # Now try to grab the symbols.
+    ac_nlist=conftest.nm
+    if AC_TRY_EVAL(NM conftest.$ac_objext \| $lt_cv_sys_global_symbol_pipe \> $ac_nlist) && test -s "$ac_nlist"; then
+      # See whether the symbols have a leading underscore.
+      if grep '^. _nm_test_func' "$ac_nlist" >/dev/null; then
+        lt_cv_sys_symbol_underscore=yes
+      else
+        if grep '^. nm_test_func ' "$ac_nlist" >/dev/null; then
+	  :
+        else
+	  echo "configure: cannot find nm_test_func in $ac_nlist" >&AS_MESSAGE_LOG_FD
+        fi
+      fi
+    else
+      echo "configure: cannot run $lt_cv_sys_global_symbol_pipe" >&AS_MESSAGE_LOG_FD
+    fi
+  else
+    echo "configure: failed program was:" >&AS_MESSAGE_LOG_FD
+    cat conftest.c >&AS_MESSAGE_LOG_FD
+  fi
+  rm -rf conftest*
+  ])
+  sys_symbol_underscore=$lt_cv_sys_symbol_underscore
+  AC_SUBST([sys_symbol_underscore])
+])# LT_SYS_SYMBOL_USCORE
