Roll src/third_party/SPIRV-Tools/src 538512e8e898..34be23373b9e (2 commits)

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git/+log/538512e8e898..34be23373b9e

git log 538512e8e898..34be23373b9e --date=short --first-parent --format='%ad %ae %s'
2020-04-09 stevenperron@google.com Handle more cases in dead member elim (#3289)
2020-04-09 h.baensch.92@gmail.com Fix pch macro to ignore clang-cl (#3283)

Created with:
  gclient setdep -r src/third_party/SPIRV-Tools/src@34be23373b9e

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/spirv-tools-chromium-autoroll
Please CC radial-bots+chrome-roll@google.com,jonahr@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Cq-Include-Trybots: luci.chromium.try:android_angle_vk32_deqp_rel_ng;luci.chromium.try:android_angle_vk32_rel_ng;luci.chromium.try:android_angle_vk64_deqp_rel_ng;luci.chromium.try:android_angle_vk64_rel_ng;luci.chromium.try:linux_angle_deqp_rel_ng;luci.chromium.try:linux-angle-rel;luci.chromium.try:win-angle-rel-32;luci.chromium.try:win-angle-rel-64;luci.chromium.try:win-angle-deqp-rel-32;luci.chromium.try:win-angle-deqp-rel-64
Bug: None
Tbr: radial-bots+chrome-roll@google.com,jonahr@google.com
Change-Id: I4da9d1a7e21e6346c423d03b6ee52bb113993272
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145434Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#758178}

DEPS

@@ -286,7 +286,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.
-  'spv_tools_revision': '538512e8e8980cc01ab6501cd1cbd402d54f8491',
+  'spv_tools_revision': '34be23373b9e73694c3b214ba857283bad65aedb',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.