[clang] [flang] [llvm] [AArch64] Add ability to list extensions enabled for a target (PR #95805)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clangd-ubuntu-tsan` running on `clangd-ubuntu-clang` while building `clang,flang,llvm` at step 6 "test-build-clangd-clangd-index-server-clangd-indexer-check-clangd".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/134/builds/680

Here is the relevant piece of the build log for the reference:
```
Step 6 (test-build-clangd-clangd-index-server-clangd-indexer-check-clangd) failure: test (failure)
******************** TEST 'Clangd :: execute-command.test' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 1: clangd -lit-test < /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/llvm-project/clang-tools-extra/clangd/test/execute-command.test | /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/build/bin/FileCheck -strict-whitespace /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/llvm-project/clang-tools-extra/clangd/test/execute-command.test
+ clangd -lit-test
+ /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/build/bin/FileCheck -strict-whitespace /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/llvm-project/clang-tools-extra/clangd/test/execute-command.test
WARNING: ThreadSanitizer: unexpected memory mapping 0x79ffffe72000-0x7a0000300000
FATAL: ThreadSanitizer: unexpectedly found incompatible memory layout.
FATAL: Please file a bug.
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/build/bin/FileCheck -strict-whitespace /vol/worker/clangd-ubuntu-clang/clangd-ubuntu-tsan/llvm-project/clang-tools-extra/clangd/test/execute-command.test

--

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


```

https://github.com/llvm/llvm-project/pull/95805