[clang] [Clang][Driver] Add new flags to control IR verification (PR #68172)

[Arthur Eubanks via cfe-commits]

================
@@ -146,6 +146,13 @@ Non-comprehensive list of changes in this release
 
 New Compiler Flags
 ------------------
+* ``-fverify-intermediate-code`` and it's complement ``-fno-verify-intermediate-code``.
+  Enables or disables verification of the generated LLVM IR.
+  It's strongly encouraged to enable this verification, as it can catch hard to
+  find code generation bugs.
----------------
aeubanks wrote:

I'd word it like "users can pass this to turn on extra verification to catch compiler bugs at the cost of extra compile time"; I agree that we shouldn't be recommending it since the cost/benefit doesn't seem worth it for production toolchains. It's useful for validating a toolchain when you update the toolchain, but probably not super impactful after that.

https://github.com/llvm/llvm-project/pull/68172