It seems to install some libraries that depend on
/usr/lib/system/libsystem_darwin.dylib, which doesn't exist.
Googling suggests it will be there in macOS 10.13,
but on Sierra or earlier, you're outta luck.
It looks like the only directly-affected PG dependency is
libxml; if you leave out --with-libxml you can still build.
I found this out the hard way on longfin's host, so I've
temporarily removed --with-libxml from that animal's
configuration to restore it to service. I trust I'll be
able to re-enable that after 10.13 comes out.
regards, tom lane