Allow snapshots to be generated without using vfp3 code on arm.

There is currently no way of specifying that the snapshot build by scons should be created without using the vfp3 instructions.
Review URL: http://codereview.chromium.org/7604031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8872 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -153,13 +153,19 @@ LIBRARY_FLAGS = {
         }
       },
       'armeabi:softfp' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=0', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=0'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=softfp'],
         }
       },
       'armeabi:hard' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=hard'],
         }
@@ -496,7 +502,10 @@ SAMPLE_FLAGS = {
         }
       },
       'armeabi:hard' : {
-        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1', 'CAN_USE_VFP_INSTRUCTIONS'],
+        'CPPDEFINES' : ['USE_EABI_HARDFLOAT=1'],
+        'vfp3:on': {
+          'CPPDEFINES' : ['CAN_USE_VFP_INSTRUCTIONS']
+        },
         'simulator:none': {
           'CCFLAGS':     ['-mfloat-abi=hard'],
         }
@@ -1090,6 +1099,12 @@ SIMPLE_OPTIONS = {
     'default': 'off',
     'help': 'compress startup data (snapshot) [Linux only]'
   },
+  'vfp3': {
+    'values': ['on', 'off'],
+    'default': 'on',
+    'help': 'use vfp3 instructions when building the snapshot [Arm only]'
+  },
+
 }
 
 ALL_OPTIONS = dict(PLATFORM_OPTIONS, **SIMPLE_OPTIONS)