Problem: libstdc++ symbols exported on Debian/[Hurd|kFreeBSD]

Solution: use the --version-script map on those systems as well, as it
is supported

Makefile.am

@@ -295,6 +295,12 @@ src_libzmq_la_LDFLAGS = \
 	@LIBZMQ_EXTRA_LDFLAGS@ \
 	-Wl,--version-script=$(srcdir)/src/libzmq.vers
 else
+if ON_GNU
+src_libzmq_la_LDFLAGS = \
+	-version-info @LTVER@ \
+	@LIBZMQ_EXTRA_LDFLAGS@ \
+	-Wl,--version-script=$(srcdir)/src/libzmq.vers
+else
 src_libzmq_la_LDFLAGS = \
 	-version-info @LTVER@ \
 	@LIBZMQ_EXTRA_LDFLAGS@ \
@@ -303,6 +309,7 @@ endif
 endif
 endif
 endif
+endif
 
 src_libzmq_la_CPPFLAGS = $(CODE_COVERAGE_CPPFLAGS) $(LIBUNWIND_CFLAGS)
 src_libzmq_la_CFLAGS = $(CODE_COVERAGE_CFLAGS) $(LIBUNWIND_CFLAGS)

configure.ac

@@ -207,6 +207,12 @@ case "${host_os}" in
         ;;
     *freebsd*)
         # Define on FreeBSD to enable all library features
+        case "${host_os}" in
+            # On Debian/kFreeBSD with gnu set the --version-script flag
+            kfreebsd*-gnu*)
+                libzmq_on_gnu="yes"
+            ;;
+        esac
         CPPFLAGS="-D__BSD_VISIBLE $CPPFLAGS"
         AC_DEFINE(ZMQ_HAVE_FREEBSD, 1, [Have FreeBSD OS])
         ;;