Disable thumb when building tcmalloc

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 1eaa390c156bd963f2066087645085a3fde47560..c4d61e2281a7662b4a3ca17b8fe92dac7d15469b 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -534,13 +534,6 @@ config("compiler_cpu_abi") {
           "-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" ]
@@ -765,6 +758,17 @@ config("compiler_arm_fpu") {
   }
 }
 
+config("compiler_arm_thumb") {
+  if (current_cpu == "arm" && arm_use_thumb && is_posix &&
+      !(is_mac || is_ios || is_nacl)) {
+    cflags = [ "-mthumb" ]
+    if (is_android && !is_clang) {
+      # Clang doesn't support this option.
+      cflags += [ "-mthumb-interwork" ]
+    }
+  }
+}
+
 # runtime_library -------------------------------------------------------------
 #
 # Sets the runtime library and associated options.