pythongh-110828: AIX 32bit build needs -latomic for _testcapi module (python#110962)

Author: ayappanec

Misc/NEWS.d/next/Build/2023-10-17-03-10-40.gh-issue-110828.31vQ9B.rst

@@ -0,0 +1 @@
+AIX 32bit needs ``-latomic`` to build the :mod:`!_testcapi` extension module.

configure

@@ -7056,7 +7056,8 @@ int main()
 ])
 
 AS_VAR_IF([ac_cv_libatomic_needed], [yes],
-          [LIBS="${LIBS} -latomic"])
+          [LIBS="${LIBS} -latomic"
+           LIBATOMIC=${LIBATOMIC-"-latomic"}])
 _RESTORE_VAR([CPPFLAGS])
 
 
@@ -7328,7 +7329,10 @@ PY_STDLIB_MOD([_hashlib], [], [test "$ac_cv_working_openssl_hashlib" = yes],
   [$OPENSSL_INCLUDES], [$OPENSSL_LDFLAGS $OPENSSL_LDFLAGS_RPATH $LIBCRYPTO_LIBS])
 
 dnl test modules
-PY_STDLIB_MOD([_testcapi], [test "$TEST_MODULES" = yes])
+PY_STDLIB_MOD([_testcapi],
+    [test "$TEST_MODULES" = yes],
+    dnl Modules/_testcapi needs -latomic for 32bit AIX build
+    [], [], [$LIBATOMIC])
 PY_STDLIB_MOD([_testclinic], [test "$TEST_MODULES" = yes])
 PY_STDLIB_MOD([_testclinic_limited], [test "$TEST_MODULES" = yes])
 PY_STDLIB_MOD([_testinternalcapi], [test "$TEST_MODULES" = yes])