Various ports are careless with their use of flags handled by make(1).
The ports framework expects ports to append, not overrwrite, certain of its flags. This is especially important for tier-2 ports.
Here is a quote from EdMaste 20180918:
There are some ports that still fail to link with LLD_UNSAFE=yes or adding -Wl,-znotext (like math/p5-Math-Pari, devel/p5-Data-MessagePack-Stream, multimedia/libfame) because they do not honour LDFLAGS. We need to either patch those ports to honour LDFLAGS, or fix the underlying -fPIC issues in those ports.
MarkLinimon used to have a tool that would walk the tree looking for flags that got stomped on. If anyone would be interested in collaborating on getting it back going again, please let him know.