Use a prebuilt clang/LLVM to make the build hermetic

LLVM version 16.0.4 was chosen for parity with our current developer
desktop setup. This can be changed later.

Upsides:
- Consistent compiler behavior across OS versions, supporting our ubuntu
  20.04 and debian 11 users.
- We can upgrade on our own schedule to a newer clang and access fancy
  new features such as c++20 and newer clang-tidy lints.

Downsides:
- Extra time / bandwidth on a fresh (`bazel clean --expunge`) build.
- We move one step further away from being a "regular debian citizen" as
  we fetch more dependencies outside of debian's own package graph.

.github/workflows/presubmit.yaml

@@ -61,7 +61,7 @@ jobs:
     - name: Setup apt
       run: apt update -y && apt upgrade -y
     - name: Install dependencies
-      run: apt install -y git clang libcurl4-openssl-dev clang-tidy
+      run: apt install -y git clang libcurl4-openssl-dev clang-tidy libtinfo5
     - name: Install bazel
       run: bash tools/buildutils/installbazel.sh
     - name: Build cvd

base/cvd/.bazelrc

@@ -1,6 +1,6 @@
 build --copt=-fdiagnostics-color=always
-build --repo_env=CC=clang
 
 build:clang-tidy --aspects @bazel_clang_tidy//clang_tidy:clang_tidy.bzl%clang_tidy_aspect
 build:clang-tidy --output_groups=report
 build:clang-tidy --@bazel_clang_tidy//:clang_tidy_config=//:clang_tidy_config
+build:clang-tidy --@bazel_clang_tidy//:clang_tidy_executable=@llvm_toolchain//:clang-tidy

base/cvd/MODULE.bazel

@@ -33,3 +33,15 @@ git_override(
     commit = "f23d924918c581c68cd5cda5f12b4f8198ac0c35",
     remote = "https://github.com/erenon/bazel_clang_tidy.git",
 )
+
+bazel_dep(name = "toolchains_llvm", version = "1.2.0")
+
+# Configure and register the toolchain.
+llvm = use_extension("@toolchains_llvm//toolchain/extensions:llvm.bzl", "llvm")
+llvm.toolchain(
+   llvm_version = "16.0.4",
+)
+
+use_repo(llvm, "llvm_toolchain")
+
+register_toolchains("@llvm_toolchain//:all")

base/debian/control

@@ -2,26 +2,27 @@ Source: cuttlefish-common
 Maintainer: Cuttlefish Team
 Section: misc
 Priority: optional
-Build-Depends: config-package-dev,
-               debhelper-compat (= 12),
+Build-Depends: bazel [amd64],
                clang,
-               pkg-config,
+               config-package-dev,
+               debhelper-compat (= 12),
+               git,
+               libcurl4-openssl-dev,
                libfmt-dev,
                libgflags-dev,
-               libjsoncpp-dev,
-               libcurl4-openssl-dev,
                libgoogle-glog-dev,
                libgtest-dev,
+               libjsoncpp-dev,
+               libtinfo5,
+               libprotobuf-c-dev,
+               libprotobuf-dev,
                libssl-dev,
                libxml2-dev,
-               uuid-dev,
-               libprotobuf-dev,
-               libprotobuf-c-dev,
-               protobuf-compiler,
                libz3-dev,
+               pkg-config,
+               protobuf-compiler,
                sed,
-               git,
-               bazel [amd64]
+               uuid-dev
 Standards-Version: 4.5.0
 
 Package: cuttlefish-base