Roll buildtools forward and fix GN build for it.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
   import("//build/config/mips.gni")
@@ skipping 35 matching lines @@
 }
 
 # compiler ---------------------------------------------------------------------
 #
 # Base compiler configuration.
 #
 # See also "runtime_library" below for related stuff and a discussion about
 # where stuff should go. Put warning related stuff in the "warnings" config.
 
 config("compiler") {
+  asmflags = []
   cflags = []
   cflags_c = []
   cflags_cc = []
   cflags_objcc = []
   ldflags = []
   defines = []
 
   # In general, Windows is totally different, but all the other builds share
   # some common GCC configuration. This section sets up Windows and the common
   # GCC flags, and then we handle the other non-Windows platforms specifically
@@ skipping 374 matching lines @@
     if (is_clang) {
       if (current_cpu == "arm") {
         cflags += [ "--target=arm-linux-androideabi" ]
         ldflags += [ "--target=arm-linux-androideabi" ]
       } else if (current_cpu == "x86") {
         cflags += [ "--target=x86-linux-androideabi" ]
         ldflags += [ "--target=x86-linux-androideabi" ]
       }
     }
   }
+
+  # Assign any flags set for the C compiler to asmflags so that they are sent
+  # to the assembler. The Windows assembler takes different types of flags
+  # so only do so for posix platforms.
+  if (is_posix) {
+    asmflags += cflags
+    asmflags += cflags_c
+  }
 }
 
 config("compiler_arm_fpu") {
   if (current_cpu == "arm") {
     cflags = [ "-mfpu=$arm_fpu" ]
   }
 }
 
 # runtime_library -------------------------------------------------------------
 #
@@ skipping 474 matching lines @@
       cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
     }
     ldflags = [ "/DEBUG" ]
   } else {
     cflags = [
       "-g3",
       "-ggdb3",
     ]
   }
 }