[README] update installation instructions for macOS (missing dependencies)

[ed9w2in6]

I believe this is an macOS issue only.

In short,

The following dependencies are also needed in addition to the current listed dependencies:

• libidn2
• librtmp

On macOS do: brew install libidn2 rtmpdump

Reason:
Both library are both GNU hence some linux distribution may ship with both of them. For instance on my Centos machine your instructions worked, in which macOS does NOT.

[j0sh]

Getting the same here on an Intel macOS machine and the 0.5.4 release. In my case, zstd was also missing.

Shouldn't these libraries be statically complied into the build? Librtmp is also unnecessary and should be omitted from the build config.

For anyone else using Nixpkgs on Mac: I got this working under a Nix shell with nix-shell -p libidn2 rtmpdump zstd and adding the library paths (discovered via pkg-config --libs) to a DYLD_FALLBACK_LIBRARY_PATH environment variable to the curl_chrome110 script. Something like this - the exact paths will vary:

DYLD_FALLBACK_LIBRARY_PATH=/nix/store/c4nas454dlkzgam9ihz0sdxqdjyjj3fi-libidn2-2.3.4/lib:/nix/store/shj1rqgqlh47xwg3mh007vbjkdvhnl49-rtmpdump-unstable-2021-02-19/lib:/nix/store/ly3wj661lbrgh5gj07kfx0y8cyqygrl0-zstd-1.5.5/lib "$dir/curl-impersonate-chrome" 

[j0sh]

Heads up that this issue still exists for MacOS. For those of you using nix on macos, the nixpkgs workaround mentioned earlier still works.

[lwthiker]

Thanks, I have taken a look and I see the problem now. The MacOS runner in GitHub comes with librtmp and libidn2 installed, and the curl build system automatically detects that and links them in. I think I'll explicitly disable them so the pre-compiled release binaries do not have them linked in (this is the case in the Linux binaries anyways).