[llvm-dev] RFC: LTO should use -disable-llvm-verifier

[Duncan P. N. Exon Smith via llvm-dev]

The verifier takes ~5% of link time when using LTO.  I think we
should add a `-disable-llvm-verifier` option to the LTO plugins, and
change the clang driver to pass the option through in release builds.
In asserts builds, the clang driver would not pass the option.

This would match the way the driver passes -disable-llvm-verifier to
-cc1.

Everyone on board?