[llvm] fix extern cl::opt definitions for DLL export (#145374)

## Purpose
This patch is one in a series of code-mods that annotate LLVM’s public
interface for export. This patch ensures a few `cl::opt` declarations
are properly annotated with `LLVM_ABI`. The annotations currently have
no meaningful impact on the LLVM build; however, they are a prerequisite
to support an LLVM Windows DLL (shared library) build.

## Background
This effort is tracked in #109483. Additional context is provided in
[this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307),
and documentation for `LLVM_ABI` and related annotations is found in the
LLVM repo
[here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst).

## Overview
- Remove local `extern` declarations of `llvm::PrintPipelinePasses`
because it is already correctly declared with an `LLVM_ABI` annotation
in `llvm\Passes\PassBuilder.h`. Leaving these declarations results in a
gcc compile warning unless they are also annotated with `LLVM_ABI`.
- Similarly, remove local `extern` declarations of
`ProfileSummaryCutoffHot` and `UseContextLessSummary` from
`llvm/tools/llvm-profgen/ProfileGenerator.cpp` since they are declared
with `LLVM_ABI` in `llvm\ProfileData\ProfileCommon.h`.
- Explicitly annotate the extern declaration of `ProfileCorrelate` in
`clang/lib/CodeGen/BackendUtil.cpp` since it is not declared in a
header. The definition of `ProfileCorrelate` in
`llvm\lib\Transforms\Instrumentation\InstrProfiling.cpp` is already
annotated with `LLVM_ABI`.

## Validation
Local builds and tests to validate cross-platform compatibility. This
included llvm, clang, and lldb on the following configurations:

- Windows with MSVC
- Windows with Clang
- Linux with GCC
- Linux with Clang
- Darwin with Clang

1 files changed, 0 insertions, 4 deletions

diff --git a/flang/lib/Frontend/FrontendActions.cpp b/flang/lib/Frontend/FrontendActions.cpp
index d684eeb..bf15def 100644
--- a/flang/lib/Frontend/FrontendActions.cpp
+++ b/flang/lib/Frontend/FrontendActions.cpp
@@ -74,10 +74,6 @@
 #include <memory>
 #include <system_error>
 
-namespace llvm {
-extern cl::opt<bool> PrintPipelinePasses;
-} // namespace llvm
-
 using namespace Fortran::frontend;
 
 constexpr llvm::StringLiteral timingIdParse = "Parse";