detectFromBuilding

pub fn detectFromBuilding(arena: Allocator, zig_lib_dir: Path, target: *const std.Target) !LibCDirs {
    const s = std.fs.path.sep_str;

    if (target.os.tag.isDarwin()) {
        const list = try arena.alloc([]const u8, 1);
        list[0] = try arena.print("{f}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "any-darwin-any", .{zig_lib_dir});
        return .{
            .libc_include_dir_list = list,
            .libc_installation = null,
            .libc_framework_dir_list = &.{},
            .sysroot = null,
            .darwin_sdk_layout = .vendored,
        };
    }

    const generic_name = libCGenericName(target);
    // Some architecture families are handled by the same set of headers.
    const arch_name = if (target.isMuslLibC() or target.isWasiLibC())
        std.zig.target.muslArchNameHeaders(target.cpu.arch)
    else if (target.isGnuLibC())
        std.zig.target.glibcArchNameHeaders(target.cpu.arch)
    else if (target.isFreeBSDLibC())
        std.zig.target.freebsdArchNameHeaders(target.cpu.arch)
    else if (target.isNetBSDLibC())
        std.zig.target.netbsdArchNameHeaders(target.cpu.arch)
    else if (target.isOpenBSDLibC())
        std.zig.target.openbsdArchNameHeaders(target.cpu.arch)
    else
        @tagName(target.cpu.arch);
    const os_name = @tagName(target.os.tag);
    const abi_name = if (target.isMuslLibC())
        std.zig.target.muslAbiNameHeaders(target.abi)
    else if (target.isGnuLibC())
        std.zig.target.glibcAbiNameHeaders(target.abi)
    else if (target.isNetBSDLibC())
        std.zig.target.netbsdAbiNameHeaders(target.abi)
    else
        @tagName(target.abi);
    const arch_include_dir = try arena.print("{f}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-{s}-{s}", .{
        zig_lib_dir, arch_name, os_name, abi_name,
    });
    const generic_include_dir = try arena.print("{f}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "generic-{s}", .{
        zig_lib_dir, generic_name,
    });
    const generic_arch_name = std.zig.target.osArchName(target);
    const arch_os_include_dir = try arena.print("{f}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-{s}-any", .{
        zig_lib_dir, generic_arch_name, os_name,
    });
    const generic_os_include_dir = try arena.print("{f}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "any-{s}-any", .{
        zig_lib_dir, os_name,
    });

    const list = try arena.alloc([]const u8, 4);
    list[0] = arch_include_dir;
    list[1] = generic_include_dir;
    list[2] = arch_os_include_dir;
    list[3] = generic_os_include_dir;

    return .{
        .libc_include_dir_list = list,
        .libc_installation = null,
        .libc_framework_dir_list = &.{},
        .sysroot = null,
        .darwin_sdk_layout = .vendored,
    };
}