Default to irt=1 for bitcode and use_sandboxed_translator=1
Default to irt=1 for bitcode and use_sandboxed_translator=1

Since we use a separate environment for building the IRT image itself, it
doesn't matter that only environments are incompatible with building it.
So use_sandboxed_translator=1 is no longer a limitation.

The pnacl linker now supports -lppapi with sufficient magic to produce
IRT-compatible nexe layouts.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1889
TEST=trybots

Review URL: http://codereview.chromium.org/7372009

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@6060 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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