Prevent any of "fixedfeaturecpu" tests to be run under pnacl.
Prevent any of "fixedfeaturecpu" tests to be run under pnacl.

Those tests fail with pnacl_generate_pexe=0 on x86-64 but we would
like to create a bot test using this mode.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2760
TEST= manual
Review URL: https://chromiumcodereview.appspot.com/10365002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@8484 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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