[3.8] bpo-40112: distutils test_search_cpp: Fix logic to determine if C compiler is xlc on AIX (GH-19225)

[miss-islington]

(cherry picked from commit 76db37b)

Co-authored-by: Michael Felt [email protected]

https://bugs.python.org/issue40112

[vstinner]

LGTM, good bot.

[miss-islington]

@aixtools and @vstinner: Status check is done, and it's a failure ❌ .

[aixtools]

@aixtools and @vstinner: Status check is done, and it's a failure ❌ .

Does not look relelated to the change:

======================================================================
ERROR: test_load_dll_with_flags (ctypes.test.test_loading.LoaderTest) [WinDLL('_sqlite3.dll', winmode=0)]

Traceback (most recent call last):
File "D:\a\1\s\lib\ctypes\test\test_loading.py", line 140, in should_pass
subprocess.check_output(
File "D:\a\1\s\lib\subprocess.py", line 411, in check_output
return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
File "D:\a\1\s\lib\subprocess.py", line 512, in run
raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['D:\a\1\s\PCbuild\amd64\python.exe', '-c', "from ctypes import *; import nt;WinDLL('_sqlite3.dll', winmode=0)"]' returned non-zero exit status 1.