[CMake] Make optimizing sanitizer builds optional

This behavior has been the default for a long time, so the default value is On, however this can make it difficult to debug sanitizer failures, so we should have an option to turn it off.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332628 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed