[llvm] [tools][llc] Add `--save-stats` option (PR #163967)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/23797

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LLVM :: tools/llc/save-stats.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 3
/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/llc -mtriple=arm64-apple-macosx --save-stats=obj -o /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/test/tools/llc/Output/save-stats.ll.tmp.s /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/test/tools/llc/save-stats.ll && cat /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/test/tools/llc/Output/save-stats.ll.tmp.stats | /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/test/tools/llc/save-stats.ll
# executed command: /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/llc -mtriple=arm64-apple-macosx --save-stats=obj -o /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/test/tools/llc/Output/save-stats.ll.tmp.s /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/test/tools/llc/save-stats.ll
# .---command stderr------------
# | /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/llc: error: unable to get target for 'arm64-apple-macosx', see --version and --triple.
# `-----------------------------
# error: command failed with exit status: 1

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/163967