update clang_linux package to Clang 5

Disable some new warning flags to get us building.

Change-Id: I10299d667b06fb61d03e52329883c634bd42f45c
Reviewed-on: https://skia-review.googlesource.com/44341
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
4 files changed