Revert "[ThinLTO] Ensure sanitizer passes are run"

This reverts commit r317715. It failed a Windows buildbot since
ThinLTO is presumably not supported, leading to a corrupt file error
on the object file:
http://lab.llvm.org:8011/builders/sanitizer-windows/builds/19395/steps/run%20check-asan/logs/stdio

Will re-commit the new ThinLTO part of the test to a linux only test
file.

llvm-svn: 317717