Ensure that release archives contain everything needed for Bazel

This change adds some files to EXTRA_DIST in Makefile.am so that our
published tar and zip files will have everything needed for Bazel
builds. I also added a basic test for this so that next time we should
find out sooner if we're missing any important files.

This should fix #9129.

Makefile.am

@@ -1424,8 +1424,10 @@ EXTRA_DIST = $(@DIST_LANG@_EXTRA_DIST)   \
   examples/list_people.py                \
   examples/list_people_test.go           \
   examples/pubspec.yaml                  \
+  maven_install.json                     \
   protobuf.bzl                           \
   protobuf_deps.bzl                      \
+  protobuf_version.bzl                   \
   third_party/zlib.BUILD                 \
   util/python/BUILD                      \
   internal.bzl

tests.sh

@@ -68,6 +68,7 @@ build_cpp_distcheck() {
   # Unzip the dist tar file.
   DIST=`ls *.tar.gz`
   tar -xf $DIST
+
   cd ${DIST//.tar.gz}
   # Check if every file exists in the dist tar file.
   FILES_MISSING=""
@@ -77,7 +78,10 @@ build_cpp_distcheck() {
       FILES_MISSING="$FILE $FILES_MISSING"
     }
   done
+  # Do a basic check that we can perform Bazel builds.
+  bazel build //:protobuf //:protobuf_java
   cd ..
+
   if [ ! -z "$FILES_MISSING" ]; then
     echo "Missing files in EXTRA_DIST: $FILES_MISSING"
     exit 1