[llvm] [RISCV] Lower llvm.clear_cache to __riscv_flush_icache for glibc targets (PR #93481)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-nvptx-nvidia-win` running on `as-builder-8` while building `llvm` at step 7 "test-build-unified-tree-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/54/builds/153

Here is the relevant piece of the build log for the reference:
```
Step 7 (test-build-unified-tree-check-llvm) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/X86/2008-05-12-tailmerge-5.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
c:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\build\bin\llc.exe < C:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\llvm-project\llvm\test\CodeGen\X86\2008-05-12-tailmerge-5.ll | c:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\build\bin\filecheck.exe C:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\llvm-project\llvm\test\CodeGen\X86\2008-05-12-tailmerge-5.ll
# executed command: 'c:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\build\bin\llc.exe'
# executed command: 'c:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\build\bin\filecheck.exe' 'C:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\llvm-project\llvm\test\CodeGen\X86\2008-05-12-tailmerge-5.ll'
# .---command stderr------------
# | C:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\llvm-project\llvm\test\CodeGen\X86\2008-05-12-tailmerge-5.ll:25:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: shll $14, %edi
# |               ^
# | <stdin>:17:21: note: scanning from here
# |  movw %r9w, 14(%rsp)
# |                     ^
# | <stdin>:19:2: note: possible intended match here
# |  shll $14, %eax
# |  ^
# | 
# | Input file: <stdin>
# | Check file: C:\buildbot\as-builder-8\llvm-nvptx-nvidia-win\llvm-project\llvm\test\CodeGen\X86\2008-05-12-tailmerge-5.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            .
# |            .
# |            .
# |           12:  movb %al, 26(%rsp) 
# |           13:  movb %ah, 27(%rsp) 
# |           14:  movw %dx, 38(%rsp) 
# |           15:  movl %ecx, 32(%rsp) 
# |           16:  movb %r8b, 13(%rsp) 
# |           17:  movw %r9w, 14(%rsp) 
# | next:25'0                         X error: no match found
# |           18:  movl 16(%rsp), %eax 
# | next:25'0     ~~~~~~~~~~~~~~~~~~~~~
# |           19:  shll $14, %eax 
# | next:25'0     ~~~~~~~~~~~~~~~~
# | next:25'1      ?               possible intended match
# |           20:  sarl $23, %eax 
# | next:25'0     ~~~~~~~~~~~~~~~~
# |           21:  cmpl 32(%rsp), %eax 
# | next:25'0     ~~~~~~~~~~~~~~~~~~~~~
# |           22:  jne LBB0_6 
# | next:25'0     ~~~~~~~~~~~~
# |           23: ## %bb.1: ## %bb27 
# | next:25'0     ~~~~~~~~~~~~~~~~~~~
...

```

https://github.com/llvm/llvm-project/pull/93481