Add some target triples for better determinism

These tests were failing on some buildbots after r206548 (reverted in
r206556), but passing locally.

They were missing target triples, so maybe that's the problem?
Reapply "blockfreq: Rewrite BlockFrequencyInfoImpl"

This reverts commit r206556, effectively reapplying commit r206548 and
its fixups in r206549 and r206550.

In an intervening commit I've added target triples to the tests that
were failing remotely [1] (but passing locally).  I'm hoping the mystery
is solved?  I'll revert this again if the tests are still failing
remotely.

[1]: http://bb.pgr.jp/builders/ninja-x64-msvc-RA-centos6/builds/1816