Update prebuilt Clang to build 4630689.

Built from version 6.0.1
based on r316199.

Bug: http://b/73127367
Test: N/A
Exempt-From-Owner-Approval: my branch
Change-Id: I2d5a99c73c6e22a1e74f21764d048e26da66b5b6
(cherry picked from commit aed01aa52ce8c1b1580e19fb7bb02298676a3035)
1876 files changed