package/monit: do not forcibly build a static binary

Static linking with glibc is not really supported, because of the NSS
libraries that are still to be dynamically-loaded at runtime.

Also, Buildroot explicitly does not support statically linking with
glibc.

Reported-by: Peter Kümmel <syntheticpp@gmx.net>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>