PNaCl driver fixes:
PNaCl driver fixes:

* Handle -pthread more carefully.
* Make sure -S, -c and -E ignore flag inputs.
* Refactor LD_ARGs to make them more consistent.
* Get rid of static glibc LD_ARG which is no longer supported.
Review URL: https://chromiumcodereview.appspot.com/9232064

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@7695 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client