Test that bazel_binaries.download matches .bazelversion (#47)

We're already testing our `.bazelversion` files are consistent. We
should make sure the Bazel binary we're running our integration tests
is consistent as well.

Author: KushalP

tests/version/bazel_version_test.sh

@@ -5,11 +5,19 @@ set -eufo pipefail
 WORKING_DIRECTORY="${1}"
 
 ROOT_BAZEL_VERSION="${WORKING_DIRECTORY}/.bazelversion"
+ROOT_BAZEL_MODULE="${WORKING_DIRECTORY}/MODULE.bazel"
 
 BAZEL_VERSIONS=$(find "${WORKING_DIRECTORY}" -name .bazelversion)
 
 for BAZEL_VERSION in ${BAZEL_VERSIONS}; do
   cmp -b "${ROOT_BAZEL_VERSION}" "${BAZEL_VERSION}"
 done
 
+if ! grep -q "bazel_binaries.download(version = \"$(cat "${ROOT_BAZEL_VERSION}")\")" "${ROOT_BAZEL_MODULE}"; then
+  echo "${ROOT_BAZEL_MODULE} 'bazel_binaries.download' version doesn't match .bazelversion"
+  echo "Expected: bazel_binaries.download(version = \"$(cat "${ROOT_BAZEL_VERSION}")\")"
+  echo "Found:    $(grep -E "^bazel_binaries.download" "${ROOT_BAZEL_MODULE}")"
+  exit 1
+fi
+
 echo "All .bazelversion files are identical"