Update V8 to r3121 as required for WebKit update.

Change-Id: Ic53e0aef9a9eb9b71ee7d25a8aef61520bba899c
diff --git a/SConstruct b/SConstruct
old mode 100644
new mode 100755
index b5aa7ab..2b2ce1d
--- a/SConstruct
+++ b/SConstruct
@@ -373,7 +373,8 @@
       'CPPDEFINES': ['V8_TARGET_ARCH_IA32']
     },
     'arch:x64': {
-      'CPPDEFINES':   ['V8_TARGET_ARCH_X64']
+      'CPPDEFINES':   ['V8_TARGET_ARCH_X64'],
+      'LINKFLAGS': ['/STACK:2091752']
     },
   }
 }
@@ -474,7 +475,7 @@
     },
     'arch:x64': {
       'CPPDEFINES': ['V8_TARGET_ARCH_X64'],
-      'LINKFLAGS': ['/MACHINE:X64']
+      'LINKFLAGS': ['/MACHINE:X64', '/STACK:2091752']
     },
     'mode:debug': {
       'CCFLAGS':   ['/Od'],