ci: flip Bazel version back to 4.0.0

ci: use default-jre

ci: set DEBIAN_FRONTEND=noninteractive

ci: use default-jdk

.github/bin/build-and-test.sh

diff --git a/.github/bin/build-and-test.sh b/.github/bin/build-and-test.sh
index f0910c7..f059ac7 100755
--- a/.github/bin/build-and-test.sh
+++ b/.github/bin/build-and-test.sh
@@ -94,7 +94,6 @@
     bazel coverage \
           --combined_report=lcov \
           --coverage_report_generator=@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main \
-          --java_runtime_version=remotejdk_11 \
           ${CHOSEN_TARGETS}
     # output will be in bazel-out/_coverage/_coverage_report.dat
     ;;

.github/settings.sh

diff --git a/.github/settings.sh b/.github/settings.sh
index 66b92a4..91028b0 100644
--- a/.github/settings.sh
+++ b/.github/settings.sh
@@ -32,7 +32,7 @@
 export BAZEL_OPTS="-c opt --show_progress_rate_limit=10.0"
 
 # Used to fetch the BAZEL version where needed.
-export BAZEL_VERSION=5.3.2
+export BAZEL_VERSION=4.0.0
 
 # TODO(b/171989992): revert to using release version after upgrading system
 #   libraries/image (need: GLIBCXX_3.4.26, CXXABI_1.3.11, GLIBC_2.29).

.github/workflows/verible-ci.yml

diff --git a/.github/workflows/verible-ci.yml b/.github/workflows/verible-ci.yml
index 7fdffdb..e492643 100644
--- a/.github/workflows/verible-ci.yml
+++ b/.github/workflows/verible-ci.yml
@@ -15,6 +15,7 @@
   BOT_USER: "Deployment Bot"
   BOT_EMAIL: "verible-dev@googlegroups.com"
   GHA_MACHINE_TYPE: "n2-standard-8"
+  DEBIAN_FRONTEND: "noninteractive"
 
 jobs:
 
@@ -154,7 +155,7 @@
       run: |
         set -x
         apt -qqy update
-        apt -qq -y install clang-10 build-essential wget git python3 python-is-python3 gcc-10 g++-10
+        apt -qq -y install clang-10 build-essential wget git python3 python-is-python3 gcc-10 g++-10 default-jdk
         source ./.github/settings.sh
         ./.github/bin/set-compiler.sh 10
         ./.github/bin/install-bazel.sh