Stub out pnacl-opt and pnacl-finalize tools for scons built_elsewhere=1

This is required to make the PSO generation test pass on ARM hardware;
(or more specifically, opt will run on the x86 bot, and get stubbed
out on the hardware bot). Stubbing out pnacl-finalize isn't
required for that particular test but is just for completeness.

Review URL:

git-svn-id: svn:// fcba33aa-ac0c-11dd-b9e7-8d5594d729c2
diff --git a/site_tools/ b/site_tools/
index 0cce6d1..2208d6d 100755
--- a/site_tools/
+++ b/site_tools/
@@ -55,7 +55,7 @@
   env.Replace(CC='true', CXX='true', LINK='true', AR='true',
               RANLIB='true', AS='true', ASPP='true', LD='true',
-              STRIP='true')
+              STRIP='true', PNACLOPT='true', PNACLFINALIZE='true')
 def _SetEnvForNativeSdk(env, sdk_path):