init

    pub fn init(arena: Allocator, io: Io, options: InitOptions) Directories {
        const wasi = builtin.target.os.tag == .wasi;
        const cwd = options.cwd;

        const zig_lib: Cache.Directory = d: {
            if (options.override_zig_lib) |path| break :d openUnresolved(arena, io, cwd, path, .@"zig lib");
            if (wasi) break :d getPreopen(options.preopens, "/lib");
            break :d findZigLibDirFromSelfExe(arena, io, cwd, options.self_exe_path) catch |err| {
                fatal("unable to find zig installation directory from executable path {q}: {t}", .{
                    options.self_exe_path, err,
                });
            };
        };
        const build_root: Cache.Directory = if (options.build_root) |s|
            openUnresolved(arena, io, cwd, s, .@"build root")
        else
            .cwd();

        const global_cache: Cache.Directory = d: {
            if (options.override_global_cache) |path| break :d openUnresolved(arena, io, cwd, path, .@"global cache");
            if (wasi) break :d getPreopen(options.preopens, "/cache");
            const path = resolveGlobalCacheDir(arena, options.environ_map) catch |err| {
                fatal("unable to resolve zig cache directory: {t}", .{err});
            };
            break :d openUnresolved(arena, io, cwd, path, .@"global cache");
        };

        const local_cache = getLocalCacheDirectory(arena, io, cwd, global_cache, options.local_cache_strat);

        if (mem.eql(u8, zig_lib.path orelse "", global_cache.path orelse "")) {
            fatal("zig lib directory '{f}' cannot be equal to global cache directory '{f}'", .{ zig_lib, global_cache });
        }
        if (mem.eql(u8, zig_lib.path orelse "", local_cache.path orelse "")) {
            fatal("zig lib directory '{f}' cannot be equal to local cache directory '{f}'", .{ zig_lib, local_cache });
        }

        return .{
            .cwd = cwd,
            .zig_lib = zig_lib,
            .global_cache = global_cache,
            .local_cache = local_cache,
            .build_root = build_root,
        };
    }