[llvm] Normalize file path to fix problems with different folder separators. (PR #215225)

[via llvm-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 139518 tests passed
* 3662 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### LLVM
<details>
<summary>LLVM.tools/llvm-objdump/XCOFF/print-linenumber.test</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 3
c:\_work\llvm-project\llvm-project\build\bin\llvm-objdump.exe -d -l C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF/Inputs/basic32.o | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF\print-linenumber.test --check-prefix=LINES32
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\llvm-objdump.exe' -d -l 'C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF/Inputs/basic32.o'
# note: command had no output on stdout or stderr
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' 'C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF\print-linenumber.test' --check-prefix=LINES32
# .---command stderr------------
# | C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF\print-linenumber.test:22:17: error: LINES32-NEXT: expected string not found in input
# | # LINES32-NEXT: ; /basic.c:1
# |                 ^
# | <stdin>:7:11: note: scanning from here
# | ; .main():
# |           ^
# | <stdin>:8:1: note: possible intended match here
# | ; \basic.c:1
# | ^
# | 
# | Input file: <stdin>
# | Check file: C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF\print-linenumber.test
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            1:  
# |            2: C:\_work\llvm-project\llvm-project\llvm\test\tools\llvm-objdump\XCOFF/Inputs/basic32.o: file format aixcoff-rs6000 
# |            3:  
# |            4: Disassembly of section .text: 
# |            5:  
# |            6: 00000000 <.main>: 
# |            7: ; .main(): 
# | next:22'0              {   search range start (exclusive)
# | next:22'1                  error: no match found in search range
# |            8: ; \basic.c:1 
# | next:22'2     ?              possible intended match
# |            9:  0: 38 60 00 00 li 3, 0 
# |           10: ; \basic.c:3 
# |           11:  4: 48 00 00 04 b 0x8 <.main+0x8> 
# |           12: ; \basic.c:4 
# |           13:  8: 4e 80 00 20 blr 
# |           14:  c: 00 00 00 00 <unknown> 
# |           15:  10: 00 00 20 40 <unknown> 
# |           16:  14: 00 00 00 01 <unknown> 
# |           17:  18: 00 00 00 0c <unknown> 
# |           18:  1c: 00 04 6d 61 <unknown> 
# |           19:  20: 69 6e 00 00 xori 14, 11, 0 
# |           20:  ... 
# | next:22'3          } search range end (exclusive)
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/215225