That's really strange. With a non-modified configure.in (which means that is containing this misplaced stanza), I did:
# cd /usr/ports/security/tor/ # make deinstall # make clean # make install
and... voilá:
mb# ldd /usr/local/bin/tor /usr/local/bin/tor: libtcmalloc.so.2 => /usr/local/lib/libtcmalloc.so.2 (0x2844e000) libz.so.5 => /lib/libz.so.5 (0x281aa000) libm.so.5 => /lib/libm.so.5 (0x281bc000) libevent-2.0.so.6 => /usr/local/lib/event2/libevent-2.0.so.6 (0x284b6000) libssl.so.7 => /usr/local/lib/libssl.so.7 (0x284f1000) libcrypto.so.7 => /usr/local/lib/libcrypto.so.7 (0x2853f000) libthr.so.3 => /lib/libthr.so.3 (0x281df000) libc.so.7 => /lib/libc.so.7 (0x28090000) libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x286a1000) libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x281f4000)
So it seems the 'make clean' did some magic. According to man ports(7):
clean Remove the expanded source code. This recurses to dependencies unless NOCLEANDEPENDS is defined.
Should I understand it was some 'expanded source code' which was breaking my local ports tree?