チュートリアルの左上にあるボタンからmasterに切り替えればよかった

ーーーーー

基本的にはこの手順で良い
https://docs.bazel.build/versions/2.0.0/tutorial/ios-app.html

ただ、依存ライブラリが古いまま（2020/1/3現在）なので若干記法などが異なる。
チュートリアルの中で出てくるWORKSPACEとBUILDを次のように変更すればとりあえずビルドまでは行ける。

WORKSPACE

workspace(name = "tutorial")

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "bazel_skylib",
    urls = [
        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.2/bazel-skylib-1.0.2.tar.gz",
        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.2/bazel-skylib-1.0.2.tar.gz",
    ],
    sha256 = "97e70364e9249702246c0e9444bccdc4b847bed1eb03c5a3ece4f83dfe6abc44",
)
load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
bazel_skylib_workspace()

# iOS basic build deps.

http_archive(
    name = "build_bazel_rules_apple",
    sha256 = "bdc8e66e70b8a75da23b79f1f8c6207356df07d041d96d2189add7ee0780cf4e",
    strip_prefix = "rules_apple-b869b0d3868d78a1d4ffd866ccb304fb68aa12c3",
    url = "https://github.com/bazelbuild/rules_apple/archive/b869b0d3868d78a1d4ffd866ccb304fb68aa12c3.tar.gz",
)

load(
    "@build_bazel_rules_apple//apple:repositories.bzl",
    "apple_rules_dependencies",
)

apple_rules_dependencies()

load(
    "@build_bazel_rules_swift//swift:repositories.bzl",
    "swift_rules_dependencies",
)

swift_rules_dependencies()

load(
    "@build_bazel_apple_support//lib:repositories.bzl",
    "apple_support_dependencies",
)

apple_support_dependencies()

BUILD

load("@build_bazel_rules_apple//apple:ios.bzl", "ios_application")

objc_library(
    name = "UrlGetClasses",
    srcs = [
         "UrlGet/AppDelegate.m",
         "UrlGet/UrlGetViewController.m",
         "UrlGet/main.m",
    ],
    hdrs = glob(["UrlGet/*.h"]),
    data = ["UrlGet/UrlGetViewController.xib"],
)

ios_application(
    name = "ios-app",
    bundle_id = "Google.UrlGet",
    families = [
        "iphone",
        "ipad",
    ],
    minimum_os_version = "9.0",
    infoplists = [":UrlGet/UrlGet-Info.plist"],
    visibility = ["//visibility:public"],
    deps = [":UrlGetClasses"],
)