Start adapting to bzlmod configurations. (carbon-language#3505)

Some background information is at https://bazel.build/external/migration

Trying to handle the simple cases first. This adds a requirement for
bazel 7 due to differences in bzlmod handling between 6 and 7 (also
discussed on
[#infra](https://discord.com/channels/655572317891461132/707150492370862090/1184942191412510720)).
Bazel seems to be okay with a partial migration such as ths.

The python import behavior has subtly shifted, so `carbon.` is no longer
part of import paths. There's a version-incompatible change for `@@`.
bzlmod makes repos sometimes show as `name~version`.

`target-determinator` seems to be okay with `@@` after a version update.

Things not moved here are things that basically need more dep work:

- clang_register_toolchains because I need to dive into its format.
- llvm-project because we need something slightly atypical, I need to
make sure patching and the repo work carries over.
- com_google_libprotobuf_mutator is sufficiently atypical that it
doesn't have a module already, but should be one of the easier things to
fix.
- brotli/woff2: I think we should actually consider removing these. But
again, they're not trivial moves.
- treesitter due to toolchain registration, which has shifted a bit.
- rules_nodejs because treesitter depends on it in an awkward way to
migrate.

.bazeliskrc

@@ -4,4 +4,4 @@
 
 # Keep pinned to a recent release, listed at
 # https://github.com/bazelbuild/bazel.
-USE_BAZEL_VERSION=6.0.0
+USE_BAZEL_VERSION=7.0.0

.bazelrc

@@ -2,10 +2,6 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# TODO: https://bazel.build/external/migration for
-# https://github.com/bazelbuild/bazel/issues/18958
-build --noenable_bzlmod
-
 # Default to using a disk cache to minimize re-building LLVM and Clang which we
 # try to avoid updating too frequently to minimize rebuild cost. The location
 # here can be overridden in the user configuration where needed.
@@ -19,25 +15,6 @@ build --disk_cache=~/.cache/carbon-lang-build-cache
 # future Bazel releases.
 build --experimental_guard_against_concurrent_changes
 
-# Allow the toolchain to configure itself differently in the host build from
-# the target build. Even when the host and target platforms are ostensibly the
-# same (and use identical toolchains), it is beneficial to be able to configure
-# the specific toolchain features enabled for the target separately from the
-# host. For example, sanitizers make sense for the target significantly more
-# than for the host.
-#
-# Bazel bug tracking undoing the default here:
-# https://github.com/bazelbuild/bazel/issues/13315
-#
-# TODO: Remove this once we require at least Bazel version 7, where
-# --incompatible_use_host_features is the default.
-build --incompatible_dont_enable_host_nonhost_crosstool_features=false
-
-# Opt into the new Bazel toolchain resolution mechanism.
-# TODO: Remove this once we require at least Bazel version 7, where it is the
-# default.
-build --incompatible_enable_cc_toolchain_resolution
-
 # Disable warnings for all external compilations. These involve code that isn't
 # developed as part of Carbon and may be difficult or impossible to patch, so
 # warnings aren't likely to be actionable.

.pre-commit-config.yaml

@@ -219,6 +219,7 @@ repos:
 # This excludes third-party code, and patches to third-party code.
 exclude: |
  (?x)^(
+ MODULE.bazel.lock|
  bazel/patches/.*\.patch|
  third_party/examples/.*/carbon/.*|
  third_party/llvm-project/.*|

MODULE.bazel

@@ -0,0 +1,64 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+"""Bazel modules."""
+
+module(name = "carbon")
+
+bazel_dep(name = "bazel_skylib", version = "1.5.0")
+bazel_dep(
+ name = "abseil-cpp",
+ version = "20230802.0",
+ repo_name = "com_google_absl",
+)
+bazel_dep(
+ name = "re2",
+ version = "2023-11-01",
+ repo_name = "com_googlesource_code_re2",
+)
+bazel_dep(
+ name = "googletest",
+ version = "1.14.0.bcr.1",
+ repo_name = "com_google_googletest",
+)
+bazel_dep(
+ name = "google_benchmark",
+ version = "1.8.3",
+ repo_name = "com_github_google_benchmark",
+)
+bazel_dep(name = "rules_bison", version = "0.2.2")
+bazel_dep(name = "rules_flex", version = "0.2.1")
+bazel_dep(name = "rules_m4", version = "0.2.3")
+bazel_dep(name = "rules_cc", version = "0.0.9")
+bazel_dep(name = "rules_proto", version = "6.0.0-rc1")
+bazel_dep(
+ name = "protobuf",
+ version = "21.7",
+ repo_name = "com_google_protobuf",
+)
+
+###############################################################################
+# Python
+###############################################################################
+
+bazel_dep(name = "rules_python", version = "0.27.1")
+
+python = use_extension("@rules_python//python/extensions:python.bzl", "python")
+python.toolchain(
+ python_version = "3.11",
+)
+use_repo(python, "python_versions")
+
+pip = use_extension(
+ "@rules_python//python/extensions:pip.bzl",
+ "pip",
+)
+
+# Create a central repo that knows about the pip dependencies.
+pip.parse(
+ hub_name = "py_deps",
+ python_version = "3.11",
+ requirements_lock = "//github_tools:requirements.txt",
+)
+use_repo(pip, "py_deps")