Avoid having a LIBS setting when compiling the V8 library

because this interferes with the shared library build.
Only prepend v8 to the LIBS list when building samples
or cctest.
Review URL: http://codereview.chromium.org/1387004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4289 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -1009,7 +1009,6 @@ def BuildSpecific(env, mode, env_overrides):
 
   # Link the object files into a library.
   env.Replace(**context.flags['v8'])
-  env.Prepend(LIBS=[library_name])
 
   context.ApplyEnvOverrides(env)
   if context.options['library'] == 'static':
@@ -1044,7 +1043,9 @@ def BuildSpecific(env, mode, env_overrides):
     sample_env.Depends(sample_program, library)
     context.sample_targets.append(sample_program)
 
-  cctest_program = env.SConscript(
+  cctest_env = env.Copy()
+  cctest_env.Prepend(LIBS=[library_name])
+  cctest_program = cctest_env.SConscript(
     join('test', 'cctest', 'SConscript'),
     build_dir=join('obj', 'test', target_id),
     exports='context object_files',