Explictly pass -marm when arm mode is required

base/allocator/BUILD.gn

Index: base/allocator/BUILD.gn
diff --git a/base/allocator/BUILD.gn b/base/allocator/BUILD.gn
index cffe6c28db26e8aabc191ad85b9e94a9f1f783e9..401519662f3f17d2f249646449eeea1d85241df4 100644
--- a/base/allocator/BUILD.gn
+++ b/base/allocator/BUILD.gn
@@ -216,18 +216,17 @@ if (use_allocator == "tcmalloc") {
       "$tcmalloc_dir/src",
     ]
 
-    configs -= [
-      "//build/config/compiler:chromium_code",
-
-      # Thumb mode disabled due to bug in clang integrated assembler
-      # TODO(https://llvm.org/bugs/show_bug.cgi?id=31058)
-      "//build/config/compiler:compiler_arm_thumb",
-    ]
+    configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [
       "//build/config/compiler:no_chromium_code",
       ":tcmalloc_flags",
     ]
 
+    # Thumb mode disabled due to bug in clang integrated assembler
+    # TODO(https://llvm.org/bugs/show_bug.cgi?id=31058)
+    configs -= [ "//build/config/compiler:compiler_arm_thumb" ]
+    configs += [ "//build/config/compiler:compiler_arm" ]
+
     # TODO(crbug.com/633719) Make tcmalloc work with AFDO if possible.
     configs -= [ "//build/config/compiler:afdo" ]