Port r282246 to gn.

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 13 matching lines @@
   #   0 means no symbols.
   symbol_level = 2
 
   # Component build.
   is_component_build = false
   # Debug build.
   is_debug = true
 
   # Set to true when compiling with the Clang compiler. Typically this is used
   # to configure warnings.
-  is_clang = (os == "mac" || os == "ios")
+  is_clang = (os == "mac" || os == "ios" || os == "linux")
 
   # Forces a 64-bit build on Windows. Does nothing on other platforms. Normally
   # we build 32-bit on Windows regardless of the current host OS bit depth.
   # Setting this flag will override this logic and generate 64-bit toolchains.
   #
   # Normally this would get set automatically when you specify a target using
   # the 64-bit toolchain. You can also set this on the command line to convert
   # the default toolchain to 64-bit.
   force_win64 = false
 
@@ skipping 424 matching lines @@
     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")
 }