Use pkg-config for including shared libzmq

[jirijakes]

Currently on FreeBSD (tried only on 14.1) fails with shared libzmq:

$> rm -rf node_modules/
$> npm install
$> npm run build --zmq-shared

[…]
Building libzmq with options  {
  zmq_shared: true,
  […]
}
[…]
ld: error: unable to find library -lzmq
c++: error: linker command failed with exit code 1 (use -v to see invocation)
gmake: *** [zeromq.target.mk:154: Release/obj.target/zeromq.node] Error 1
[…]

The problem is that linking with -lzmq is not sufficient on FreeBSD, it requires -L/usr/local/lib -lzmq. Using pkg-config might help.

After applying this patch, it builds.

On FreeBSD 14.1:

$> pkg-config --libs libzmq
-L/usr/local/lib -lzmq

On Linux:

$> pkg-config --libs libzmq
-lzmq

---

Might help #639 by allowing to use shared libzmq.

[aminya]

This should be guarded for platforms that do not ship pkg-config (e.g. Windows). Also, on Windows, the library is probably called zmq not libzmq

[jirijakes]

Ah, makes sense. Will look into it!

[aminya]

Any updates on this? @jirijakes

[jirijakes]

Apologies for the delayed response.

I have not got to it yet but still plan to within next few weeks. Is it okay to keep the PR open in the meantime?

[aminya]

I have migrated the build to CMake/vcpkg. So we no longer maintain a gyp based build. I am gausing that the FreeBSD builds will now be successful under CMake. Let me know if you face any issues.