Instead of this, do:

PATHFIX_MAKEFILEIN=    Makefile.am

By default, Uses/pathfix.mk alters Makefile.in. By switching to USES=autoreconf, you need to tell it to alter Makefile.am rather than Makefile.in, which either doesn't exist or gets overwritten.

Is gcrypt usable with OpenSSL? I thought they were, in general, mutually exclusive?

Exactly what https://www.freebsd.org/doc/en/books/porters-handbook/uses-pathfix.html says :-)

I am not particularly familiar with this, but it builds fine with both OPENSSL and GCRYPT options enabled (with GNUTLS option disabled). In fact, comparing the libraries built when using the OPENSSL option, with and without the GNUTLS option, the libraries link against the following additional libraries with GNUTLS enabled:

+       libgcrypt.so.20 => /usr/local/lib/libgcrypt.so.20 (0x80246b000)
+       libgpg-error.so.0 => /usr/local/lib/libgpg-error.so.0 (0x80277d000)
+       libintl.so.8 => /usr/local/lib/libintl.so.8 (0x802bb9000)

So it appears that it both builds ok with OPENSSL and GCRYPT, and also links to additional libraries. Happy to take direction here as to whether this should be changed.