build: enable V8 undefined double support

Enable V8_ENABLE_UNDEFINED_DOUBLE in the V8 GYP configuration,
matching the setting added on main by 8394db3.

This is a candidate for the repeated wrong-map deoptimizations in
big.js reported in #66717. Preserve the existing v26 GYP settings
and apply only the undefined double feature configuration.

Refs: 8394db3
Refs: #66717
Signed-off-by: inoway46 <inoueyuya416@gmail.com>
Assisted-by: Codex

Author: inoway46

tools/v8_gypfiles/features.gypi

@@ -294,6 +294,9 @@
     # ReadOnlySpace.
     'v8_enable_extensible_ro_snapshot%': 1,
 
+    # Use the encoding of undefined in double values.
+    'v8_enable_undefined_double%': 1,
+
     # Variables from v8.gni
 
     # Enable ECMAScript Internationalization API. Enabling this feature will
@@ -524,6 +527,9 @@
       ['v8_enable_extensible_ro_snapshot==1', {
         'defines': ['V8_ENABLE_EXTENSIBLE_RO_SNAPSHOT',],
       }],
+      ['v8_enable_undefined_double==1', {
+        'defines': ['V8_ENABLE_UNDEFINED_DOUBLE',],
+      }],
       ['v8_enable_leaptiering==1', {
         'defines': ['V8_ENABLE_LEAPTIERING',],
       }],