ports-mgmt/pkg 2.7.4 might need libmd one more time on 16.0-CURRENT

I only saw this strange behaviour on my own laptop running a week old 16.0-CURRENT, but here’s one way of coping. Simply add -lmd after $(STATIC_LDFLAGS) of ports-mgmt/pkg/files/patch-src_Makefile.autosetup, like this: