[GN] Fix -g flags to be consistent between gyp & gn on iOS.

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")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 1320 matching lines @@
     }
     if (is_win_fastlink && visual_studio_version != "2013") {
       # Tell VS 2015+ to create a PDB that references debug
       # information in .obj and .lib files instead of copying
       # it all. This flag is incompatible with /PROFILE
       ldflags = [ "/DEBUG:FASTLINK" ]
     } else {
       ldflags = [ "/DEBUG" ]
     }
   } else {
-    cflags = [ "-g2" ]
+    if (is_ios) {
+      cflags = [ "-gdwarf-2" ]
+    } else {
+      cflags = [ "-g2" ]
+    }
     if (use_debug_fission) {
       cflags += [ "-gsplit-dwarf" ]
     }
     asmflags = cflags
     ldflags = []
   }
 }
 
 # Minimal symbols.
 config("minimal_symbols") {
@@ skipping 41 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }