test: Mock out MAC address access

This makes it possible for our ethernet interfaces to have MAC Addresses
detected and configured for testing without the system providing a real
NIC.

Change-Id: Ie985efec0a5e393b0b76f3d02bd3015fef6349e4
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/Makefile.am b/test/Makefile.am
index 388f679..842f8ca 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -37,7 +37,7 @@
 
 test_CPPFLAGS = ${generic_cpp_flags}
 test_CXXFLAGS = ${generic_cxx_flags}
-test_LDFLAGS  = ${generic_ld_flags}
+test_LDFLAGS  = ${generic_ld_flags} -ldl
 
 test_dns_updater_CPPFLAGS = ${generic_cpp_flags}
 test_dns_updater_CXXFLAGS = ${generic_cxx_flags}