[clang] [Clang][Driver] Fix compiler-rt library directory for cygwin (PR #208925)

[via cfe-commits]

github-actions[bot] wrote:

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

* 55750 tests passed
* 1384 tests skipped
* 1 test failed

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

### Clang
<details>
<summary>Clang.Driver/cygwin-print-file-name.c</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 3
c:\_work\llvm-project\llvm-project\build\bin\clang.exe --sysroot=C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/basic_cygwin_tree         -resource-dir=C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/resource_dir         --target=x86_64-pc-windows-cygnus         -print-file-name=libclang_rt.builtins-x86_64.a       | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe --check-prefix=CHECK C:\_work\llvm-project\llvm-project\clang\test\Driver\cygwin-print-file-name.c
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' '--sysroot=C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/basic_cygwin_tree' '-resource-dir=C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/resource_dir' --target=x86_64-pc-windows-cygnus -print-file-name=libclang_rt.builtins-x86_64.a
# note: command had no output on stdout or stderr
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' --check-prefix=CHECK 'C:\_work\llvm-project\llvm-project\clang\test\Driver\cygwin-print-file-name.c'
# .---command stderr------------
# | C:\_work\llvm-project\llvm-project\clang\test\Driver\cygwin-print-file-name.c:8:11: error: CHECK: expected string not found in input
# | // CHECK: {{.*}}/lib/cygwin/libclang_rt.builtins-x86_64.a
# |           ^
# | <stdin>:1:1: note: scanning from here
# | C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/resource_dir\lib\cygwin\libclang_rt.builtins-x86_64.a
# | ^
# | <stdin>:1:71: note: possible intended match here
# | C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/resource_dir\lib\cygwin\libclang_rt.builtins-x86_64.a
# |                                                                       ^
# | 
# | Input file: <stdin>
# | Check file: C:\_work\llvm-project\llvm-project\clang\test\Driver\cygwin-print-file-name.c
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |            1: C:\_work\llvm-project\llvm-project\clang\test\Driver/Inputs/resource_dir\lib\cygwin\libclang_rt.builtins-x86_64.a 
# | check:8'0    {                                                                                                                  } search range (exclusive bounds)
# | check:8'1                                                                                                                         error: no match found in search range
# | check:8'2                                                                           ?                                             possible intended match
# | >>>>>>
# `-----------------------------
# 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/208925