- Move getLibExtraCFlags/getLibExtraCxxFlags/getLibExtraLdFlags/getLibExtraLibs from LibraryPackage to Package base class so ToolPackage can also use them
- Full ToolPackage implementation: getBuildRootPath, getIncludeDir, getLibDir, getBinDir, getToolField with platform suffix support
- Update PackageBuilder to support building ToolPackage (not just LibraryPackage)
- Update PackageInstaller: support ToolPackage in download/extract/install pipeline, auto-install build-time tools, record installed versions
- Allow LibraryPackage|ToolPackage union type in all Executor classes and UnixShell::initializeEnv