With the introduction of this flag, it is no longer necessary to enable noundef analysis with 4 separate flags.
(-Xclang -enable-noundef-analysis -mllvm -msan-eager-checks=1).
This change only covers the introduction into the compiler.
This is a follow up to: https://reviews.llvm.org/D116855
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D116633
Kevin Athey