net-snmp: fix "libtool --finish"

LIB_LDCONFIG_CMD failed since it is using a host dir $(libdir)
which is /usr/lib64 does not exist on host when compile 64bit
image.

In fact, configuring dynamic linker run-time bindings is meaningless
at this step,  If it is needed, Poky would write ldconfig scripts to
rpm-postinst for each recipe while do_package, in package.bbclass.

Signed-off-by: Roy.Li <rongqing.li@windriver.com>
Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>