[llvm] [lit] Use `.format()` over format strings literals (PR #155912)

[Vladimir Vereschaka via llvm-commits]

vvereschaka wrote:

@justinfargnoli , here is a trace output on Windows for that part of code:
```
[0/1] Running the LLVM regression testsllvm-lit.py: C:\buildbot\temp\llvm-project\llvm\utils\lit\lit\llvm\config.py:57: note: using lit tools: C:\Program Files\Git\usr\bin
+++ c:/buildbot/latest-cuda/bin/ptxas.exe -m 32
--- (stdout): ptxas fatal   : Value ' 32' is not defined for option 'machine'

--- (stderr):
llvm-lit.py: C:\buildbot\temp\llvm-project\llvm\utils\lit\lit\TestingConfig.py:157: fatal: unable to parse config file 'C:\\buildbot\\temp\\llvm-project\\llvm\\test/lit.cfg.py', traceback: Traceback (most recent call last):
  File "C:\buildbot\temp\llvm-project\llvm\utils\lit\lit\TestingConfig.py", line 145, in load_from_path
    exec(compile(data, path, "exec"), cfg_globals, None)
  File "C:\buildbot\temp\llvm-project\llvm\test/lit.cfg.py", line 444, in <module>
    enable_ptxas(ptxas_executable)
  File "C:\buildbot\temp\llvm-project\llvm\test/lit.cfg.py", line 436, in enable_ptxas
    if ptxas_supports_address_size_32(ptxas_executable):
  File "C:\buildbot\temp\llvm-project\llvm\test/lit.cfg.py", line 413, in ptxas_supports_address_size_32
    raise RuntimeError("Unexpected ptxas output: {}".format(result.stderr))
RuntimeError: Unexpected ptxas output:
```

the error message goes to stdout when using Win version of `ptxas`, but not to stderr. Looks like you need to check both output or merge them and check together at once.

https://github.com/llvm/llvm-project/pull/155912