build: allow enabling the --trace-maps flag in V8

This can be useful for tracing map creation.

PR-URL: nodejs#14018
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Refael Ackermann <[email protected]>

configure

@@ -288,6 +288,11 @@ parser.add_option('--enable-d8',
     dest='enable_d8',
     help=optparse.SUPPRESS_HELP)  # Unsupported, undocumented.
 
+parser.add_option('--enable-trace-maps',
+    action='store_true',
+    dest='trace_maps',
+    help='Enable the --trace-maps flag in V8 (use at your own risk)')
+
 parser.add_option('--v8-options',
     action='store',
     dest='v8_options',
@@ -956,6 +961,7 @@ def configure_v8(o):
   o['variables']['v8_random_seed'] = 0  # Use a random seed for hash tables.
   o['variables']['v8_promise_internal_field_count'] = 1 # Add internal field to promises for async hooks.
   o['variables']['v8_use_snapshot'] = 'false' if options.without_snapshot else 'true'
+  o['variables']['v8_trace_maps'] = 1 if options.trace_maps else 0
   o['variables']['node_use_v8_platform'] = b(not options.without_v8_platform)
   o['variables']['node_use_bundled_v8'] = b(not options.without_bundled_v8)
   o['variables']['force_dynamic_crt'] = 1 if options.shared else 0

node.gyp

@@ -1,6 +1,7 @@
 {
   'variables': {
     'v8_use_snapshot%': 'false',
+    'v8_trace_maps%': 0,
     'node_use_dtrace%': 'false',
     'node_use_lttng%': 'false',
     'node_use_etw%': 'false',