package/stress-ng: disable libbsd on static build

package/stress-ng: disable libbsd on static build

Static link with libbsd fails because of multiple definition of the
strlcpy symbol. uClibc optionally provides these symbols.

Add make options that disable all libbsd tests when linking statically.

Fixes:
http://autobuild.buildroot.net/results/2c77271b33c9d0e9a39cced2eda6d0df0d6b8124/
http://autobuild.buildroot.net/results/2f98c5d9ca907dd62b30bedfe4e52b014bb3e8d1/
http://autobuild.buildroot.net/results/51c4c065b93a6d11f6b4583f80f932481518905a/

Cc: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>