Update prebuilt Clang to build 4639204. am: 3244418701 am: a8c99a5205
am: b6ce230f59

Bug: http://b/68397894
Test: N/A

Change-Id: I5c269536b7f1b2ca7101094ca8d61ad31870abc9
(cherry picked from commit a8e9c9fe08d0d7039aa2778480ea7efda00232eb)
2120 files changed