autotest: Make the "ltp" test comile on ARM.

- Add a utility function to wrap "./configure" to pass appropriate "--host",
  "--target", and "--build" options to configure.
- Change the ltp test to use said utility
- Workaround an internal compiler error in "ltp".  The epoll-ltp.c test
  writes zero to an uint64_t through an unaligned pointer.  This causes our
  compiler to die.  The behavior is undefined by the C standard (C99 Section
  6.3.2.3) and I suspect that even if it did compile it would cause a "bus
  error" on ARM.  I replaced the assignment with a call to memset.

TEST=Built for x86-generic and arm-generic
BUG=None

Review URL: http://codereview.chromium.org/1161005
3 files changed