tweaks to kythe build script

-ignore failing build targets, kythe has its own bad builds logic
   A fresh index with 95% of targets is better than an old index
   with 100% stale targets.
-write latest.txt to GCS bucket after uploading entries

Change-Id: I40276c6347474c71a2c06aede806601856eadbe1

linux-x86_64/kythe/studio/build_studio_kythe.sh

diff --git a/linux-x86_64/kythe/studio/build_studio_kythe.sh b/linux-x86_64/kythe/studio/build_studio_kythe.sh
index 64ab1ad..8e292f6 100755
--- a/linux-x86_64/kythe/studio/build_studio_kythe.sh
+++ b/linux-x86_64/kythe/studio/build_studio_kythe.sh
@@ -22,8 +22,10 @@
 TARGETS="$(cat tools/base/bazel/build_targets)"
 
 # Build all targets and run the kythe extractor via extra_actions.
-tools/base/bazel/bazel build \
-  --experimental_action_listener=${EAL} -- ${TARGETS}
+# ignore failures in the build as Kythe will do statistical analysis
+# on build and produce indexes for builds with 95% coverage and up.
+tools/base/bazel/bazel build --keep_going \
+  --experimental_action_listener=${EAL} -- ${TARGETS} || true
 
 # Find all generated kythe index files.
 KINDEXES=$(find bazel-out/local-fastbuild/extra_actions/ \
@@ -44,4 +46,8 @@
 if [ -n "${GSBUCKET}" ]; then
   TIMESTAMP=$(date +'%s')
   gsutil -m cp "${OUT_ENTRIES}/*" "${GSBUCKET}/${TIMESTAMP}/"
+  LATEST_FILE="$(mktemp)"
+  echo ${TIMESTAMP}>"${LATEST_FILE}"
+  gsutil cp "${LATEST_FILE}" "${GSBUCKET}/latest.txt"
+  rm "${LATEST_FILE}"
 fi
\ No newline at end of file