Add network namespace isolation, macOS CI, and Windows build support for fwTPM

[dgarske]

Summary

• Eliminate flaky fwtpm-socket CI failures by running tests in a Linux network namespace (unshare --user --net) with fixed port 2321
• Add macOS CI: remove *darwin* configure exclusion, fix CMake pthread/rt linking, add fwtpm-macos-socket matrix entry
• Add Windows build-only support: Winsock2 portability in fwtpm_io.c, signal() fallback in fwtpm_main.c, ws2_32 linking, CMake CI entry

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR improves fwTPM portability and CI robustness by isolating socket-based tests in Linux network namespaces, expanding CI coverage to macOS, and adding Windows build-only support (Winsock + CMake linking).

Changes:

• Run fwTPM socket tests under unshare --user --net and introduce a “fixed port” mode for CI stability.
• Enable macOS CI for socket transport and adjust build/link flags for CMake.
• Add Windows build-only support via Winsock initialization/cleanup, signal handling fallback, and ws2_32 linking.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
tests/fwtpm_check.sh	Adds “fixed port” mode vs. random port selection for fwTPM socket tests.
src/fwtpm/fwtpm_main.c	Uses signal() on Windows and sigaction on POSIX for shutdown handling.
src/fwtpm/fwtpm_io.c	Introduces Winsock send/recv paths, WSAStartup/WSACleanup, and closes via CloseSocket.
configure.ac	Enables fwTPM default on macOS and blocks TIS/SHM transport on Windows with a clear error.
CMakeLists.txt	Adjusts link libraries for UNIX/macOS and adds ws2_32 for Windows.
.github/workflows/sanitizer.yml	Runs sanitizer job under network namespace and forces fixed port mode.
.github/workflows/fwtpm-test.yml	Adds macOS test matrix entry; uses namespace isolation when available; tweaks package install/ldconfig behavior.
.github/workflows/cmake-build.yml	Adds a Windows CMake build matrix entry and gates Linux-only package installation.

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