5.0.0-beta.4 - Compile fixes for FreeBSD

What's Changed

Compile fixes for FreeBSD by @hoanga in #251

FreeBSD uses the Darwin-compatible sigaction layout

(__sigaction_u.__sa_handler) and has native TCSASOFT.

Extend the Linux readpassphrase implementation to cover FreeBSD so linux_readpassphrase is available when needed.

$ uname -a
FreeBSD nori 15.1-RELEASE-p5 FreeBSD 15.1-RELEASE-p5 releng/15.1-n283639-893c7c99b60d GENERIC amd64

$ swift -version
Swift version 6.5-dev (LLVM 323c7575daad203, Swift fa911731cf90e3d)
Target: x86_64-unknown-freebsd14.3
Build config: +assertions

$ swift build
Building for debugging...
[Using on-disk description]

Build complete! (2.41 secs)

$ swift test
Building for debugging...
[Using on-disk description]

Build complete! (2.50 secs)
Test Suite 'All tests' started at 2026-11-12 21:49:35.609
Test Suite 'Debug-freebsd-x86_64.xctest' started at 2026-11-12 21:49:35.620
Test Suite 'Debug-freebsd-x86_64.xctest' passed at 2026-11-12 21:49:35.620
         Executed 0 tests, with 0 failures (0 unexpected) in 0.0 (0.0) seconds
Test Suite 'All tests' passed at 2026-11-12 21:4…

…

This patch was released by @gwynne

Full Changelog: 5.0.0-beta.3...5.0.0-beta.4