Add SCons build option to control Microsoft Visual C++ link-time code generation

SConstruct

 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 142 matching lines @@
       'CPPDEFINES':   ['_DEBUG', 'ENABLE_DISASSEMBLER', 'DEBUG'],
       'LINKFLAGS':    ['/DEBUG'],
       'msvcrt:static': {
         'CCFLAGS': ['/MTd']
       },
       'msvcrt:shared': {
         'CCFLAGS': ['/MDd']
       }
     },
     'mode:release': {
-      'CCFLAGS':      ['/O2', '/GL'],
-      'LINKFLAGS':    ['/OPT:REF', '/OPT:ICF', '/LTCG'],
-      'ARFLAGS':      ['/LTCG'],
+      'CCFLAGS':      ['/O2'],
+      'LINKFLAGS':    ['/OPT:REF', '/OPT:ICF'],
       'msvcrt:static': {
         'CCFLAGS': ['/MT']
       },
       'msvcrt:shared': {
         'CCFLAGS': ['/MD']
+      },
+      'msvcltcg:on': {
+        'CCFLAGS':      ['/GL'],
+        'LINKFLAGS':    ['/LTCG'],
+        'ARFLAGS':      ['/LTCG'],
       }
     },
   }
 }
 
 
 V8_EXTRA_FLAGS = {
   'gcc': {
     'all': {
       'CXXFLAGS':     [], #['-fvisibility=hidden'],
@@ skipping 172 matching lines @@
       'LIBS': ['winmm', 'ws2_32']
     },
     'library:shared': {
       'CPPDEFINES': ['USING_V8_SHARED']
     },
     'prof:on': {
       'LINKFLAGS': ['/MAP']
     },
     'mode:release': {
       'CCFLAGS':   ['/O2'],
-      'LINKFLAGS': ['/OPT:REF', '/OPT:ICF', '/LTCG'],
+      'LINKFLAGS': ['/OPT:REF', '/OPT:ICF'],
       'msvcrt:static': {
         'CCFLAGS': ['/MT']
       },
       'msvcrt:shared': {
         'CCFLAGS': ['/MD']
+      },
+      'msvcltcg:on': {
+        'CCFLAGS':      ['/GL'],
+        'LINKFLAGS':    ['/LTCG'],
       }
     },
     'mode:debug': {
       'CCFLAGS':   ['/Od'],
       'LINKFLAGS': ['/DEBUG'],
       'msvcrt:static': {
         'CCFLAGS': ['/MTd']
       },
       'msvcrt:shared': {
         'CCFLAGS': ['/MDd']
@@ skipping 88 matching lines @@
     'help': 'enable profiling of build target'
   },
   'library': {
     'values': ['static', 'shared'],
     'default': 'static',
     'help': 'the type of library to produce'
   },
   'msvcrt': {
     'values': ['static', 'shared'],
     'default': 'static',
-    'help': 'the type of MSVCRT library to use'
+    'help': 'the type of Microsoft Visual C++ runtime library to use'
+  },
+  'msvcltcg': {
+    'values': ['on', 'off'],
+    'default': 'on',
+    'help': 'use Microsoft Visual C++ link-time code generation'
   },
   'wordsize': {
     'values': ['64', '32'],
     'default': WORDSIZE_GUESS,
     'help': 'the word size'
   },
   'simulator': {
     'values': ['arm', 'none'],
     'default': 'none',
     'help': 'build with simulator'
@@ skipping 279 matching lines @@
 # version of scons.  Also, there's a bug in some revisions that
 # doesn't allow this flag to be set, so we swallow any exceptions.
 # Lovely.
 try:
   SetOption('warn', 'no-deprecated')
 except:
   pass
 
 
 Build()