Refactor NaCl IRT toolchains, use arm-nacl-clang

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 1a7df3025fa011bbc8e1c257f3169229c99594ae..0d32081b502c635e8b8fc06b135321818f7a60e3 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -403,19 +403,22 @@ config("compiler") {
         ]
       }
     } 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 += [
@@ -697,7 +700,7 @@ config("compiler") {
 }
 
 config("compiler_arm_fpu") {
-  if (current_cpu == "arm" && !is_ios) {
+  if (current_cpu == "arm" && !is_ios && !is_nacl) {
     cflags = [ "-mfpu=$arm_fpu" ]
   }
 }