Fix redefinition of _GNU_SOURCE

Already defined on the commandline by the Makefile.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Fix make install when no modules

If no modules, the 'install -m' will generate an error.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>