Build v8 in debug mode, we build everything else in debug.

build/SConscript.v8

 # Copyright (c) 2006-2008 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 os
 
 Import('env')
 
 # Grab the -j flag from the outer environment, if available.
 try:
   cpus = env.GetOption('num_jobs')
   cpu_flag = ' -j%d' % cpus
 except AttributeError:
   cpu_flag = ''
 
 env = env.Clone(
-    V8_MODE = 'release',
+    V8_MODE = 'debug',
     V8_MODE_DIR = '$V8_DIR/obj/$V8_MODE',
     V8_SCONS_COM = '$PYTHON $SCONS $SCONSFLAGS mode=$V8_MODE',
     SCONS='$CHROME_SRC_DIR/third_party/scons/scons.py',
     SCONSFLAGS = ('-Q '
                   '-C $OBJ_ROOT/v8 '
                   '-Y $CHROME_SRC_DIR/v8 '
                   '--warn=no-deprecated '
                   '--warn=no-no-parallel-support' + cpu_flag),
 )
 
 # Rather than build v8 with our own commands, we just shell out to v8's
 # own SCons-based build, since their build system is complicated.
 # This SConscript just declares dependencies on the outputs of that build.
 #
 # Arrange to make sure the build directory exists, since the subsidiary
 # SCons we invoke will chdir there of its own accord.
 
 if not os.path.exists(env.Dir('$OBJ_ROOT/v8').abspath):
   Mkdir(env.Dir('$OBJ_ROOT/v8').abspath)
 
 
 v8_scons_targets_off = [
-    '$V8_DIR/shell${PROGSUFFIX}',
-    '$V8_DIR/${LIBPREFIX}v8${LIBSUFFIX}',
+    '$V8_DIR/shell_g${PROGSUFFIX}',
+    '$V8_DIR/${LIBPREFIX}v8_g${LIBSUFFIX}',
     '$V8_MODE_DIR/mksnapshot${PROGSUFFIX}',
     '$V8_MODE_DIR/libraries${OBJSUFFIX}',
     '$V8_MODE_DIR/snapshot-empty${OBJSUFFIX}',
 ]
 
 v8_scons_targets_on = [
     '$V8_MODE_DIR/libraries-empty${OBJSUFFIX}',
     '$V8_MODE_DIR/snapshot${OBJSUFFIX}',
 ]
 
@@ skipping 20 matching lines @@
 env.Install('$V8_DIR', '$V8_MODE_DIR/snapshot-empty${OBJSUFFIX}')
 
 # To satisfy tests expecting the following .exe name.
 if env['PLATFORM'] == 'win32':
   # TODO(evanm): this may be necessary on other platforms(?)
   i = env.InstallAs('$TARGET_ROOT/v8_shell_sample${PROGSUFFIX}', v8[0])
 
 env.ChromeStaticLibrary('v8_snapshot',
                         ['$V8_MODE_DIR/libraries-empty${OBJSUFFIX}',
                          '$V8_MODE_DIR/snapshot${OBJSUFFIX}'])