[clang] [flang] [llvm] Reapply "Introduce -fexperimental-loop-fusion to clang and flang (PR #158844)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-4` while building `clang,flang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/27531

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 1
/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll | /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# .---command stderr------------
# | PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
# | Stack dump:
# | 0.	Program arguments: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli -jit-kind=orc-lazy -compile-threads=2 -thread-entry hello /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# |  #0 0x0000000103186440 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f0a440)
# |  #1 0x00000001031841f0 llvm::sys::RunSignalHandlers() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f081f0)
# |  #2 0x0000000103186f40 SignalHandler(int, __siginfo*, void*) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100f0af40)
# |  #3 0x000000019b7c7584 (/usr/lib/system/libsystem_platform.dylib+0x18047b584)
# |  #4 0x0000010102ce164c
# |  #5 0x0000000102ceca9c llvm::orc::ExecutionSession::removeJITDylibs(std::__1::vector<llvm::IntrusiveRefCntPtr<llvm::orc::JITDylib>, std::__1::allocator<llvm::IntrusiveRefCntPtr<llvm::orc::JITDylib>>>) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100a70a9c)
# |  #6 0x0000000102cec84c llvm::orc::ExecutionSession::endSession() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100a7084c)
# |  #7 0x0000000102d78398 llvm::orc::LLJIT::~LLJIT() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100afc398)
# |  #8 0x0000000102d7cd24 llvm::orc::LLLazyJIT::~LLLazyJIT() (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100b00d24)
# |  #9 0x0000000102284e68 runOrcJIT(char const*) (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100008e68)
# | #10 0x0000000102280598 main (/Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/lli+0x100004598)
# | #11 0x000000019b40b154
# `-----------------------------
# error: command failed with exit status: -11
# executed command: /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /Volumes/RAMDisk/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root/llvm-project/llvm/test/ExecutionEngine/OrcLazy/multiple-compile-threads-basic.ll
# `-----------------------------
# error: command failed with exit status: 2

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/158844