update clang_linux to Clang 7

Change-Id: I4f311b21de42b9f0689b9a0a488728e34ea4d332
Reviewed-on: https://skia-review.googlesource.com/155563
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed