[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 `llvm-clang-win-x-armv7l` running on `as-builder-1` while building `llvm` at step 9 "test-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/38/builds/6256

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

```
Step 9 (test-check-llvm) failure: Test just built components: check-llvm completed (failure)
******************** TEST 'LLVM :: tools/llc/save-stats.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 3
c:\buildbot\as-builder-1\x-armv7l\build\bin\llc.exe -mtriple=arm64-apple-macosx --save-stats=obj -o C:\buildbot\as-builder-1\x-armv7l\build\test\tools\llc\Output\save-stats.ll.tmp.s C:\buildbot\as-builder-1\x-armv7l\llvm-project\llvm\test\tools\llc\save-stats.ll && cat C:\buildbot\as-builder-1\x-armv7l\build\test\tools\llc\Output\save-stats.ll.tmp.stats | c:\buildbot\as-builder-1\x-armv7l\build\bin\filecheck.exe C:\buildbot\as-builder-1\x-armv7l\llvm-project\llvm\test\tools\llc\save-stats.ll
# executed command: 'c:\buildbot\as-builder-1\x-armv7l\build\bin\llc.exe' -mtriple=arm64-apple-macosx --save-stats=obj -o 'C:\buildbot\as-builder-1\x-armv7l\build\test\tools\llc\Output\save-stats.ll.tmp.s' 'C:\buildbot\as-builder-1\x-armv7l\llvm-project\llvm\test\tools\llc\save-stats.ll'
# .---command stderr------------
# | c:\buildbot\as-builder-1\x-armv7l\build\bin\llc.exe: 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