Update vm scripts to handle existing kbuilder user.

PiperOrigin-RevId: 311751972

tools/vm/build.sh

@@ -71,7 +71,7 @@ declare internal=""
 declare -r start=$(date +%s)
 declare -r end=$((${start}+${timeout}))
 while [[ "$(date +%s)" -lt "${end}" ]] && [[ "${success}" -lt 3 ]]; do
-  echo -n "."
+  echo -n "." >&2
   if gcloud compute ssh --zone "${ZONE}" "${USERNAME}"@"${INSTANCE_NAME}" -- true 2>/dev/null; then
     success=$((${success}+1))
   elif gcloud compute ssh --internal-ip --zone "${ZONE}" "${USERNAME}"@"${INSTANCE_NAME}" -- true 2>/dev/null; then

tools/vm/defs.bzl

@@ -60,7 +60,7 @@ def _vm_image_impl(ctx):
     # Run the builder to generate our output.
     echo = ctx.actions.declare_file(ctx.label.name)
     resolved_inputs, argv, runfiles_manifests = ctx.resolve_command(
-        command = "echo -ne \"#!/bin/bash\\necho $(%s)\\n\" > %s && chmod 0755 %s" % (
+        command = "echo -ne \"#!/bin/bash\\nset -e\\nimage=$(%s)\\necho ${image}\\n\" > %s && chmod 0755 %s" % (
             ctx.files.builder[0].path,
             echo.path,
             echo.path,

tools/vm/ubuntu1604/40_kokoro.sh

@@ -43,14 +43,14 @@ done
 # junitparser is used to merge junit xml files.
 pip install junitparser
 
-# We need a kbuilder user.
-if useradd -c "kbuilder user" -m -s /bin/bash kbuilder; then
-    # User was added successfully; we add the relevant SSH keys here.
-    mkdir -p ~kbuilder/.ssh
-    (IFS=$'\n'; echo "${ssh_public_keys[*]}") > ~kbuilder/.ssh/authorized_keys
-    chmod 0600 ~kbuilder/.ssh/authorized_keys
-    chown -R kbuilder ~kbuilder/.ssh
-fi
+# We need a kbuilder user, which may already exist.
+useradd -c "kbuilder user" -m -s /bin/bash kbuilder || true
+
+# We need to provision appropriate keys.
+mkdir -p ~kbuilder/.ssh
+(IFS=$'\n'; echo "${ssh_public_keys[*]}") > ~kbuilder/.ssh/authorized_keys
+chmod 0600 ~kbuilder/.ssh/authorized_keys
+chown -R kbuilder ~kbuilder/.ssh
 
 # Give passwordless sudo access.
 cat > /etc/sudoers.d/kokoro <<EOF