Update prebuilt Clang to build 4639204.

Built from version 6.0.1
based on r316199.
Test: N/A
Exempt-From-Owner-Approval: my branch
Change-Id: Ib9ef80de12edf8c21c80b2e021248d66d8757699
(cherry picked from commit 3244418701332914de33816fb6a9ba255aab26ba)
2120 files changed