Fix MinGW build

SConstruct

 # Copyright 2010 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 636 matching lines @@
 def GuessToolchain(os):
   tools = Environment()['TOOLS']
   if 'gcc' in tools:
     return 'gcc'
   elif 'msvc' in tools:
     return 'msvc'
   else:
     return None
 
 
+def GuessVisibility(os, toolchain):
+  if os == 'win32' and toolchain == 'gcc':
+    # MinGW can't do it.
+    return 'default'
+  else:
+    return 'hidden'
+
+
 OS_GUESS = utils.GuessOS()
 TOOLCHAIN_GUESS = GuessToolchain(OS_GUESS)
 ARCH_GUESS = utils.GuessArchitecture()
+VISIBILITY_GUESS = GuessVisibility(OS_GUESS, TOOLCHAIN_GUESS)
 
 
 SIMPLE_OPTIONS = {
   'toolchain': {
     'values': ['gcc', 'msvc'],
     'default': TOOLCHAIN_GUESS,
     'help': 'the toolchain to use (%s)' % TOOLCHAIN_GUESS
   },
   'os': {
     'values': ['freebsd', 'linux', 'macos', 'win32', 'android', 'openbsd', 'solaris'],
@@ skipping 85 matching lines @@
     'default': 'dumb',
     'help': 'the console to use for the d8 shell'
   },
   'verbose': {
     'values': ['on', 'off'],
     'default': 'off',
     'help': 'more output from compiler and linker'
   },
   'visibility': {
     'values': ['default', 'hidden'],
-    'default': 'hidden',
-    'help': 'shared library symbol visibility'
+    'default': VISIBILITY_GUESS,
+    'help': 'shared library symbol visibility (%s)' % VISIBILITY_GUESS
   },
   'pgo': {
     'values': ['off', 'instrument', 'optimize'],
     'default': 'off',
     'help': 'select profile guided optimization variant',
   }
 }
 
 
 def GetOptions():
@@ skipping 360 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()