Refactor NaCl IRT toolchains, use arm-nacl-clang

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")
 import("//build/config/chrome_build.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ skipping 385 matching lines @@
           # Else building libyuv gives clang's register allocator issues,
           # see llvm.org/PR15798 / crbug.com/233709
           "-momit-leaf-frame-pointer",
 
           # Align the stack on 16-byte boundaries, http://crbug.com/418554.
           "-mstack-alignment=16",
           "-mstackrealign",
         ]
       }
     } else if (current_cpu == "arm") {
-      cflags += [
-        "-march=$arm_arch",
-        "-mfloat-abi=$arm_float_abi",
-      ]
+      if (!is_nacl) {
+        cflags += [
+          "-march=$arm_arch",
+          "-mfloat-abi=$arm_float_abi",
+        ]
+        if (arm_use_thumb) {
+          cflags += [ "-mthumb" ]
+          if (is_android && !is_clang) {
+            # Clang doesn't support this option.
+            cflags += [ "-mthumb-interwork" ]
+          }
+        }
+      }
       if (arm_tune != "") {
         cflags += [ "-mtune=$arm_tune" ]
       }
-      if (arm_use_thumb) {
-        cflags += [ "-mthumb" ]
-        if (is_android && !is_clang) {  # Clang doesn't support this option.
-          cflags += [ "-mthumb-interwork" ]
-        }
-      }
       if (!is_clang) {
         # Clang doesn't support these flags.
         cflags += [
           # The tree-sra optimization (scalar replacement for
           # aggregates enabling subsequent optimizations) leads to
           # invalid code generation when using the Android NDK's
           # compiler (r5-r7). This can be verified using
           # webkit_unit_tests' WTF.Checked_int8_t test.
           "-fno-tree-sra",
 
@@ skipping 261 matching lines @@
       ]
     }
   }
 
   # Pass the same C/C++ flags to the objective C/C++ compiler.
   cflags_objc += cflags_c
   cflags_objcc += cflags_cc
 }
 
 config("compiler_arm_fpu") {
-  if (current_cpu == "arm" && !is_ios) {
+  if (current_cpu == "arm" && !is_ios && !is_nacl) {
     cflags = [ "-mfpu=$arm_fpu" ]
   }
 }
 
 # runtime_library -------------------------------------------------------------
 #
 # Sets the runtime library and associated options.
 #
 # How do you determine what should go in here vs. "compiler" above? Consider if
 # a target might choose to use a different runtime library (ignore for a moment
@@ skipping 700 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }