[gn] Use //build/config/clang/clang.gni instead of clang_toolchain.gni

Change-Id: Ie0ebf2e086d1af6a5b002b69715700949a08d4bd
diff --git a/yasm_assemble.gni b/yasm_assemble.gni
index b84f4fd..677ae5a 100644
--- a/yasm_assemble.gni
+++ b/yasm_assemble.gni
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/toolchain/clang_toolchain.gni")
+import("//build/config/clang/clang.gni")
 
 # This provides the yasm_assemble() template which uses YASM to assemble
 # assembly files.