package/haproxy: fix static only build

Add a patch to avoid dlfcn.h use when the toolchain is static only.

Fixes:
http://autobuild.buildroot.net/results/98caf66e8a7f72ee24e4d39f3aab541f82310369/
http://autobuild.buildroot.net/results/3024eb48a026b1a91e39f7d996be3d7f50314762/
http://autobuild.buildroot.net/results/e6bbf1469926bde9057f270940d1455e0f758e0e/



Cc: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>