Validate the assembly code that Subzero generates in unit tests.

Validate the assembly code that Subzero generates in unit tests.

Add RUN lines to applicable lit tests to pipe the output of Subzero (in
-Om1 and/or -O2 mode) to llvm-mc for validation.

Note that the following unit tests fail the validation:
 * callindirect.pnacl.ll
 * mangle.ll
 * nacl-other-intrinsics.ll

BUG=none
R=stichnot@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=927cc17

[Jim Stichnoth, 2014-07-22 22:00:05]

LGTM, except that we don't want to add new tests that fail.  Better to add a fix
and a test in a separate CL.

[wala, 2014-07-22 22:03:05]

Committed patchset #2 manually as r927cc17 (presubmit successful).