Use clang as host compiler on android with gn too.

build/config/BUILDCONFIG.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.
 
 # =============================================================================
 # BUILD FLAGS
 # =============================================================================
 #
 # This block lists input arguments to the build, along with their default
 # values. GN requires listing them explicitly so it can validate input and have
@@ skipping 437 matching lines @@
     host_toolchain = "//build/toolchain/win:32"
   }
 
   if (cpu_arch == "x64") {
     set_default_toolchain("//build/toolchain/win:64")
   } else if (cpu_arch == "x86") {
     set_default_toolchain("//build/toolchain/win:32")
   }
 } else if (is_android) {
   # Use clang for the x86/64 Linux host builds.
-  # (Disabled until the Clang build works properly.)
-  #if (build_cpu_arch == "x86" || build_cpu_arch == "x64") {
-  #  host_toolchain = "//build/toolchain/linux:clang_$build_cpu_arch"
-  #} else {
+  if (build_cpu_arch == "x86" || build_cpu_arch == "x64") {
+    host_toolchain = "//build/toolchain/linux:clang_$build_cpu_arch"
+  } else {
     host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
-  #}
+  }
   set_default_toolchain("//build/toolchain/android:$cpu_arch")
 } else if (is_linux) {
   if (is_clang) {
     host_toolchain = "//build/toolchain/linux:clang_$build_cpu_arch"
     set_default_toolchain("//build/toolchain/linux:clang_$cpu_arch")
   } else {
     host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
     set_default_toolchain("//build/toolchain/linux:$cpu_arch")
   }
 } else if (is_mac) {
   host_toolchain = "//build/toolchain/mac:clang"
   set_default_toolchain(host_toolchain)
 } else if (is_ios) {
   host_toolchain = "//build/toolchain/mac:host_clang"
   set_default_toolchain("//build/toolchain/mac:clang")
 }