Add GNU/Hurd cmake configuration

cmake/os/GNU.cmake

+# Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA 
+
+# This file includes GNU/Hurd specific options and quirks, related to system checks
+
+# Something that needs to be set on legacy reasons
+SET(_GNU_SOURCE 1)
+SET(CMAKE_REQUIRED_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} -D_GNU_SOURCE=1)
+
+# Ensure we have clean build for shared libraries
+# without unresolved symbols
+# Not supported with AddressSanitizer and ThreadSanitizer
+IF(NOT WITH_ASAN AND NOT WITH_TSAN)
+  SET(LINK_FLAG_NO_UNDEFINED "-Wl,--no-undefined")
+ENDIF()
+
+# 64 bit file offset support flag
+SET(_FILE_OFFSET_BITS 64)