freeswitch: declare indirect deps with linkage

[chenrui333]

• Have you followed the guidelines for contributing?
• Have you ensured that your commits follow the commit style guide?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula>)? If this is a new formula, does it pass brew audit --new <formula>?

---

https://github.com/Homebrew/homebrew-core/actions/runs/10072544121/job/27856413659?pr=178285#step:4:990

[chenrui333]

/tmp/freeswitch--libks-20240724-31202-c4fkcp/src/ks_thread.c:80:9: error: incompatible pointer to integer conversion returning 'pthread_t _Nonnull' (aka 'struct _opaque_pthread_t *') from a function with result type 'ks_pid_t' (aka 'int') [-Wint-conversion]
        return pthread_self();
               ^~~~~~~~~~~~~~
1 error generated.

• MacOS build libks error signalwire/libks#204

[chenrui333]

close for now.