Enhance macOS compatibility with spawn-based multiprocessing

[gamesh411]

Enables the full analyzer and web test suites to run on macOS by switching from fork to spawn as the multiprocessing start method on non-Linux platforms, and making the test suite cross-platform.

CodeChecker currently only runs CI on Linux. macOS uses fork by default but it is unsafe (Obj-C runtime crashes in child processes, see #4893 ), and the test suite has several Linux-specific assumptions (/tmp path, LD_PRELOAD, ld_logger, compile_commands.json command format, fixed time.sleep for task state transitions). This PR addresses all of these so the existing test suite passes on macOS with no behavioral changes on Linux.

Changes

Implementation

1. Remove compatibility.multiprocessing shim, use multiprocess directly.
   The custom compatibility wrapper is replaced with direct imports from the multiprocess package.
   The spawn start method is set explicitly in cli.py:main() on macOS/Windows.
   Spawn workers get explicit logger setup and shared state propagation (compiler_info dict) since they don't inherit parent state via fork.

2. Spawn-based worker processes in the server.
   On macOS/Windows, API and task worker processes cannot inherit the HTTPServer instance or shared Queue/Value objects.
   The server is reconstructed in spawned API workers from serializable config (_build_worker_server), and SyncManager.Queue() is used for the task queue so it can be pickled to spawned task workers.

3. arguments list format in compile_commands.json.
   The JSON compilation database spec allows entries to use either command (string) or arguments (list).
   The intercept-build wrapper used on macOS (via bear) produces the arguments form. tu_collector now normalizes both formats wherever the build action command is accessed.

4. CI worker count override.
   CC_TEST_API_WORKERS and CC_TEST_TASK_WORKERS env vars map to --api-handler-processes and --task-worker-processes server flags.
   On macOS CI, spawn workers are expensive (each re-imports the full Python stack), so constraining to 1 worker reduces resource pressure.
   Also improves wait_for_server_start with an HTTP port-based fallback and fail-fast diagnostics.

Test infra

• os.path.realpath('/tmp') to handle macOS /tmp being a symlink to /private/tmp
• Skip LD_PRELOAD/LD_LIBRARY_PATH/-m32 tests on macOS (not applicable)
• Skip gcc analyzer test when g++ is an Apple clang shim
• -fsyntax-only in buildcmd escaping tests (linking may fail with Homebrew clang@14)
• Normalize intercept-build vs ld-logger output strings for cross-platform comparison
• Normalize gcc/infer diagnostic quoting and type annotations across versions
• OAuth mock server: bind to 127.0.0.1, poll for readiness instead of fixed sleep,
  track and terminate in teardown
• Blame tests: restore cwd in finally block to prevent test pollution
• Task management tests: poll for state transitions instead of fixed sleeps
  (spawn workers take ~42s to start), use 5s tasks to reliably observe RUNNING state

GH Actions

• install-deps-macos.sh: installs llvm@14, gcc@13, cppcheck, bear, and Infer.
  Creates an intercept-build wrapper around bear (LLVM's libear.dylib seems broken on macOS ARM64 with SIP),
  gcc/g++ symlinks matching Linux naming,
  and sets SDKROOT/MACOSX_DEPLOYMENT_TARGET/CC/CXX for correct compilation and SARIF output.
• test.yml: macOS matrix entries for analyzer and tools jobs,
  separate web-macos job (sqlite only, reduced worker counts). All macOS jobs use continue-on-error.