build: add configure option to debug only Node.js part of the binary

configure.py

@@ -89,6 +89,11 @@
     dest='debug',
     help='also build debug build')
 
+parser.add_option('--debug-node',
+    action='store_true',
+    dest='debug_node',
+    help='build the Node.js part of the binary with debugging symbols')
+
 parser.add_option('--dest-cpu',
     action='store',
     dest='dest_cpu',
@@ -975,6 +980,7 @@ def configure_node(o):
   o['variables']['node_prefix'] = options.prefix
   o['variables']['node_install_npm'] = b(not options.without_npm)
   o['variables']['node_report'] = b(not options.without_report)
+  o['variables']['debug_node'] = b(options.debug_node)
   o['default_configuration'] = 'Debug' if options.debug else 'Release'
 
   host_arch = host_arch_win() if os.name == 'nt' else host_arch_cc()

node.gypi

@@ -271,6 +271,16 @@
         ],
       },
     }],
+    [ 'debug_node=="true"', {
+      'cflags!': [ '-O3' ],
+      'cflags': [ '-g', '-O0' ],
+      'defines': [ 'DEBUG' ],
+      'xcode_settings': {
+        'OTHER_CFLAGS': [
+          '-g', '-O0'
+        ],
+      },
+    }],
     [ 'coverage=="true" and node_shared=="false" and OS in "mac freebsd linux"', {
       'cflags!': [ '-O3' ],
       'ldflags': [ '--coverage',