Add CMake support for Swift targets and test configurations

[mitras-git]

Add CMake build support to the project to enable toolchain integration and bootstrapping compatibility.

Motivation:

Currently, swift-log does not support building with CMake. This addition resolves issue #484, allowing swift-log to be resolved and compiled within CMake-based environments (like the repos swift-certificates and swift-argument-parser which aer mentioned in the issue).

Modifications:

1. Project Root Config: Added CMakeLists.txt configuring the CMake project with Swift 6 and C, alongside setting up compiler flags for MSVC runtime library on Windows.
2. Helper Modules: Added the cmake/ folder:
   • SwiftSupport.cmake: dylib/module installations and triple detection helper.
   • SwiftLogConfig.cmake.in: package config export templates.
3. Target CMake Configurations: Created:
   • Sources/Logging/CMakeLists.txt & Sources/InMemoryLogging/CMakeLists.txt to define the library targets. Included generator expressions pointing INTERFACE_INCLUDE_DIRECTORIES to target output directories for Xcode generator support.
   • Tests/LoggingTests/CMakeLists.txt & Tests/InMemoryLoggingTests/CMakeLists.txt to declare test targets as loadable MODULE .xctest bundles on Apple platforms, linking toolchain Testing framework and macro plugins.
4. SwiftPM Exclusions: Excluded the new CMake files from target targets inside Package.swift and Package@swift-6.1.swift to keep SwiftPM targets warning-free.

Result:

• SwiftPM: All 164 unit tests compile and pass successfully under swift test with no warnings.
• CMake: Successfully compiles (** BUILD SUCCEEDED **) under Xcode generator (cmake -B build -G Xcode && cmake --build build).

Issue Tracking:

Fixes #484