[buildtools] roll new toolchain

Change-Id: I4a4651393fb99fadf5a344c5792bcf6566e027ec
diff --git a/fuchsia.ensure b/fuchsia.ensure
index e9770ab..a5a839f 100644
--- a/fuchsia.ensure
+++ b/fuchsia.ensure
@@ -23,7 +23,7 @@
 
 # Clang
 @Subdir clang
-fuchsia/clang/${platform} git_revision:9f48b4cda1fd734ad9ce3fe49c27fabbf31d58a7
+fuchsia/clang/${platform} git_revision:a40dc377f2f109fbe3147019ea6daec914d2587c
 
 # Go
 @Subdir go