modules/nsid: fix linkage on some systems

This is my mistake.  I was convinced this line wasn't needed
and I deleted it before merging the module.
Apparently we still have some deficiencies in the build system,
but let's defer that to migration (to meson probably).

modules/nsid/nsid.mk

 nsid_CFLAGS := -fPIC
+nsid_LDFLAGS := -Wl,-undefined -Wl,dynamic_lookup
 nsid_SOURCES := modules/nsid/nsid.c
 nsid_DEPEND := $(libkres)
 nsid_LIBS := $(contrib_TARGET) $(libkres_TARGET) $(libkres_LIBS)