[drake_bazel_...] Cleanups for bazel version

drake_bazel_download and drake_bazel_external:
- Install bazelisk (instead of using the bazel apt site) so that
  we can pin to a specific version. We use a separate script for
  this so that users have control over whether or not they want
  to install our version (and so that file_sync_test retains its
  governance over various files).
- Use .bazelversion (not .bazeliskrc) to pin a bazel version.
  When using bazelisk, this is the more canonical approach.
  Cover the version dotfile with file_sync_test.
- Upgrade bazel to latest release 7.4.1.
- Add missing file_sync_test coverage of ci_build_test.

drake_bazel_external:
- Opt-out of bzlmod.

drake_cmake_external:
- Remove unnecessary bazel installation.

.github/workflows/bazel_download.yml

@@ -17,6 +17,10 @@ jobs:
         working-directory: drake_bazel_download
         run: .github/ubuntu_setup
         shell: bash
+      - name: install_bazelisk
+        working-directory: drake_bazel_download
+        run: setup/install_bazelisk
+        shell: bash
       - name: bazel_download build and test
         working-directory: drake_bazel_download
         run: .github/ci_build_test

Jenkinsfile

@@ -22,6 +22,9 @@ node('linux-jammy-unprovisioned') {
           stage('bazel_external setup') {
             sh '.github/setup'
           }
+          stage('bazel_external bazelisk') {
+            sh 'setup/install_bazelisk'
+          }
           stage('bazel_external build and test') {
             sh '.github/ci_build_test'
           }

drake_bazel_download/.bazelversion

@@ -0,0 +1 @@
+7.4.1

drake_bazel_download/README.md

@@ -14,6 +14,11 @@ First, install the required Ubuntu packages:
 sudo setup/install_prereqs
 ```
 
+If you don't already have bazel or bazelisk installed, then install bazelisk:
+```
+sudo setup/install_bazelisk
+```
+
 Then, to build and test all apps:
 ```
 bazel test //...

drake_bazel_download/setup/install_bazelisk

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# TODO(jwnimmer-tri) Drake's install_prereqs script should offer to perform
+# this install step for us, but it doesn't -- so we need this work-around
+# in the meantime.
+
+set -euxo pipefail
+
+if [[ "${EUID:-}" -ne 0 ]]; then
+  echo 'This script must be run as root' >&2
+  exit 2
+fi
+
+wget -O bazelisk.deb \
+  https://github.com/bazelbuild/bazelisk/releases/download/v1.24.0/bazelisk-amd64.deb
+dpkg -i bazelisk.deb
+rm -f bazelisk.deb

drake_bazel_download/setup/install_prereqs

@@ -59,15 +59,3 @@ tar -xf drake.tar.gz -C /opt
 echo -e "\ndrake VERSION.TXT: $(cat /opt/drake/share/doc/drake/VERSION.TXT)\n"
 
 /opt/drake/share/drake/setup/install_prereqs
-
-apt-get install --no-install-recommends gnupg
-
-apt-key adv --fetch-keys https://bazel.build/bazel-release.pub.gpg
-echo 'deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8' \
-  > /etc/apt/sources.list.d/bazel.list
-
-apt-get update
-apt-get install --no-install-recommends $(cat <<EOF
-  bazel
-EOF
-)

drake_bazel_external/.bazelrc

@@ -1,5 +1,9 @@
 # SPDX-License-Identifier: MIT-0
 
+# Don't use bzlmod yet.
+common --enable_workspace=true
+common --enable_bzlmod=false
+
 # Default to an optimized build.
 build --compilation_mode=opt
 

drake_bazel_external/.bazelversion

@@ -0,0 +1 @@
+7.4.1

drake_bazel_external/README.md

@@ -13,6 +13,11 @@ First, install the required Ubuntu packages:
 sudo setup/install_prereqs
 ```
 
+If you don't already have bazel or bazelisk installed, then install bazelisk:
+```
+sudo setup/install_bazelisk
+```
+
 Then, to build and test all apps:
 ```
 bazel test //...

drake_bazel_external/setup/install_bazelisk

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# TODO(jwnimmer-tri) Drake's install_prereqs script should offer to perform
+# this install step for us, but it doesn't -- so we need this work-around
+# in the meantime.
+
+set -euxo pipefail
+
+if [[ "${EUID:-}" -ne 0 ]]; then
+  echo 'This script must be run as root' >&2
+  exit 2
+fi
+
+wget -O bazelisk.deb \
+  https://github.com/bazelbuild/bazelisk/releases/download/v1.24.0/bazelisk-amd64.deb
+dpkg -i bazelisk.deb
+rm -f bazelisk.deb

drake_bazel_external/setup/install_prereqs

@@ -74,15 +74,8 @@ echo -e "\ndrake VERSION.TXT: $(cat /opt/drake/share/doc/drake/VERSION.TXT)\n"
 
 /opt/drake/share/drake/setup/install_prereqs
 
-apt-get install --no-install-recommends gnupg
-
-apt-key adv --fetch-keys https://bazel.build/bazel-release.pub.gpg
-echo 'deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8' \
-  > /etc/apt/sources.list.d/bazel.list
-
 apt-get update
 apt-get install --no-install-recommends $(cat <<EOF
-  bazel
   cmake
   default-jdk
   file

drake_cmake_external/setup/install_prereqs

@@ -74,15 +74,8 @@ echo -e "\ndrake VERSION.TXT: $(cat /opt/drake/share/doc/drake/VERSION.TXT)\n"
 
 /opt/drake/share/drake/setup/install_prereqs
 
-apt-get install --no-install-recommends gnupg
-
-apt-key adv --fetch-keys https://bazel.build/bazel-release.pub.gpg
-echo 'deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8' \
-  > /etc/apt/sources.list.d/bazel.list
-
 apt-get update
 apt-get install --no-install-recommends $(cat <<EOF
-  bazel
   cmake
   default-jdk
   file

private/test/file_sync_test.py

@@ -46,6 +46,10 @@
         "drake_cmake_installed/LICENSE",
         "drake_cmake_installed_apt/LICENSE",
     ),
+    (
+        "drake_bazel_download/.github/ci_build_test",
+        "drake_bazel_external/.github/ci_build_test",
+    ),
     (
         "drake_bazel_external/.github/setup",
         "drake_cmake_external/.github/setup",
@@ -54,6 +58,14 @@
         "drake_bazel_external/setup/install_prereqs",
         "drake_cmake_external/setup/install_prereqs",
     ),
+    (
+        "drake_bazel_download/.bazelversion",
+        "drake_bazel_external/.bazelversion",
+    ),
+    (
+        "drake_bazel_download/setup/install_bazelisk",
+        "drake_bazel_external/setup/install_bazelisk",
+    ),
 )
 
 found_errors = False