libassuan duplicate symbol

[Ralph Seichter]

* Werner Koch via Gnupg-devel:

> The SO name changed for libassuan.  Do you have an old version also
> installed (should be libassuan.0.dylib) and this is accidently used
> in the build?

There was an older libassuan version in /opt/local/lib, courtesy of
dependencies pulled in by MacPorts' "wget" port:

  --->  Computing dependencies for wget
  The following dependencies will be installed:
   gnupg2
   gpgme
   libassuan

Although the old library did not seem to be referenced by my own build,
I removed the listed ports including libassuan, just to be sure.  Alas,
my build still breaks due to duplicate symbols.

I don't see any mention of the old name in my build logs (line breaks
added for improved readability):

  $ grep -E .libassuan\..+\.dylib' intel-2.5.0.log
  libtool: link: gcc -dynamiclib -Wl,-undefined -Wl,dynamic_lookup -o
  .libs/libassuan.9.dylib
  .libs/libassuan_la-assuan.o
  .libs/libassuan_la-context.o
  .libs/libassuan_la-system.o
  .libs/libassuan_la-debug.o
  .libs/libassuan_la-conversion.o
  .libs/libassuan_la-sysutils.o
  .libs/libassuan_la-client.o
  .libs/libassuan_la-server.o
  .libs/libassuan_la-assuan-error.o
  .libs/libassuan_la-assuan-buffer.o
  .libs/libassuan_la-assuan-handler.o
  .libs/libassuan_la-assuan-inquire.o
  .libs/libassuan_la-assuan-listen.o
  .libs/libassuan_la-assuan-pipe-server.o
  .libs/libassuan_la-assuan-socket-server.o
  .libs/libassuan_la-assuan-pipe-connect.o
  .libs/libassuan_la-assuan-socket-connect.o
  .libs/libassuan_la-assuan-uds.o
  .libs/libassuan_la-assuan-logging.o
  .libs/libassuan_la-assuan-socket.o
  .libs/libassuan_la-system-posix.o
  .libs/libassuan_la-assuan-io.o
  .libs/memrchr.o -L/tmp/gpgosx-2.5.0/x86_64-dist/lib
  /tmp/gpgosx-2.5.0/x86_64-dist/lib/libgpg-error.dylib -arch x86_64 -m64
  -isysroot
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
  -mmacosx-version-min=10.12 -O0 -arch x86_64
  -install_name /tmp/gpgosx-2.5.0/x86_64-dist/lib/libassuan.9.dylib
  -compatibility_version 10 -current_version 10.1

See https://seichter.de/tmp/intel-2.5.0.log for the complete, unedited
build log.

-Ralph