A std::vector causes a heap allocation and a memcpy of static
initialization data from the rodata section.
Use a static array instead so we can use the static data directly.
A colleague observes that switching the default value of
LLVM_EXPERIMENTAL_DEBUGINFO_ITERATORS to "On" hasn't flipped the value
in their CMakeCache.txt. This probably means that everyone with an
existing build tree is going to not have support built in, meaning
everyone in LLVM would need to clean+rebuild their worktree when we flip
the switch on... which doesn't sound good.
So instead, just delete the flag and everything it does, making everyone
build and run ~400 lit tests in RemoveDIs mode. None of the buildbots
have had trouble with this, so it Should Be Fine (TM).
(Sending for review as this is changing various comments, and touches
several different areas -- I don't want to get too punchy).
In Bazel, Clang current separates the clang executable into a
clang-driver library, and the actual clang executable. This allows
downstream users to make their own variations of clang, without having
to redo/maintain separate build pipelines.
This adds the same for opt for both CMake and Bazel.
