Backport all build-related commits from master to stable-0.2

This is a squash of the following commits that are required to
make gitiles buildable with the latest bazel:

9374f0a - Remove bazel-genfiles from .gitignore
bd0c596 - Use bazelisk as first choice for mvn.sh
9d5cb21 - Replace references to bazel-genfiles with bazel-bin
268d677 - Bazel: Bump bazel version to 1.0.0
03cd750 - Bazel: rules_python must be loaded now
10641da - Upgrade bazlets to latest master revision
06d3ee0 - Bazel: Introduce .bazelversion and update to 0.29.1
3de4f96 - Format all build files with buildifier
a267c30 - Bazel: Add fixes for --incompatible_load_java_rules_from_bzl
4d4432d - Upgrade bazlets to latest master revision
422d67a - Align Eclipse settings with Eclipse 2019.06
008bf1b - Update bazlets to latest revision on master

Change-Id: I4894d7beee21a0ea4bfd92c6ce3c6bf6477ef639

tools/bazelisk_version.bzl

diff --git a/tools/bazelisk_version.bzl b/tools/bazelisk_version.bzl
new file mode 100644
index 0000000..d8b3d10
--- /dev/null
+++ b/tools/bazelisk_version.bzl
@@ -0,0 +1,16 @@
+_template = """
+load("@bazel_skylib//lib:versions.bzl", "versions")
+
+def check_bazel_version():
+  versions.check(minimum_bazel_version = "{version}")
+""".strip()
+
+def _impl(repository_ctx):
+    repository_ctx.symlink(Label("@//:.bazelversion"), ".bazelversion")
+    bazelversion = repository_ctx.read(".bazelversion").strip()
+
+    repository_ctx.file("BUILD", executable = False)
+
+    repository_ctx.file("check.bzl", executable = False, content = _template.format(version = bazelversion))
+
+bazelisk_version = repository_rule(implementation = _impl)