Update prebuilt Clang to build 4639204.

Change-Id: I456b400bc534de579078665a48ae5235869fb3f3
(cherry picked from commit e39b43b081f94e1959615fb42300b65f3361ca07)
diff --git a/current/toolchains/darwin-x86_64/llvm b/current/toolchains/darwin-x86_64/llvm
index 9a6f46e..34cc306 120000
--- a/current/toolchains/darwin-x86_64/llvm
+++ b/current/toolchains/darwin-x86_64/llvm
@@ -1 +1 @@
-../../../../clang/host/darwin-x86/clang-4630689
\ No newline at end of file
+../../../../clang/host/darwin-x86/clang-4639204
\ No newline at end of file
diff --git a/current/toolchains/linux-x86_64/llvm b/current/toolchains/linux-x86_64/llvm
index 0401025..c66a1a6 120000
--- a/current/toolchains/linux-x86_64/llvm
+++ b/current/toolchains/linux-x86_64/llvm
@@ -1 +1 @@
-../../../../clang/host/linux-x86/clang-4630689
\ No newline at end of file
+../../../../clang/host/linux-x86/clang-4639204
\ No newline at end of file
diff --git a/current/toolchains/windows-x86_64/llvm b/current/toolchains/windows-x86_64/llvm
index 0e5ca67..dc98484 120000
--- a/current/toolchains/windows-x86_64/llvm
+++ b/current/toolchains/windows-x86_64/llvm
@@ -1 +1 @@
-../../../../clang/host/windows-x86/clang-4630689
\ No newline at end of file
+../../../../clang/host/windows-x86/clang-4639204
\ No newline at end of file
diff --git a/current/toolchains/windows/llvm b/current/toolchains/windows/llvm
index e500fb8..4aed1c3 120000
--- a/current/toolchains/windows/llvm
+++ b/current/toolchains/windows/llvm
@@ -1 +1 @@
-../../../../clang/host/windows-x86_32/clang-4630689
\ No newline at end of file
+../../../../clang/host/windows-x86_32/clang-4639204
\ No newline at end of file