Add third_party/llvm-build/Release+Asserts to remote inputs.

This change (
https://chromium-review.googlesource.com/c/chromium/src/+/2633051) requires the libstc++ library under third_party/llvm-build/Release+Asserts to be uploaded, and explicitly set to be included in remote action uploads.

Bug: 1169195
Change-Id: Ib7f8427d7bbb42db96d6cb907d0518d2696f2859
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2642860Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#845700}

buildtools/reclient_cfgs/rewrapper_linux.cfg

@@ -2,3 +2,4 @@ platform=container-image=docker://gcr.io/cloud-marketplace/google/rbe-ubuntu16-0
 server_address=unix:///tmp/reproxy.sock
 labels=type=compile,compiler=clang,lang=cpp
 exec_strategy=remote_local_fallback
+inputs=third_party/llvm-build/Release+Asserts