[libc++][AIX] Alignment of bool on AIX is 1

[sfertile]

Summary

Update test so that we check for a 1 byte alignment on AIX PPC32.

[sfertile]

Rebased to trigger CI.

libcxx/test/std/utilities/meta/meta.unary.prop.query/alignment_of.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// Fails for 32-bit builds on AIX.
-// UNSUPPORTED: LIBCXX-AIX-FIXME
-
 // type_traits
 
 // alignment_of
 
 #include <type_traits>
 #include <cstdint>
 
 #include "test_macros.h"
int main(int, char**)
     test_alignment_of<int*, sizeof(intptr_t)>();
     test_alignment_of<const int*, sizeof(intptr_t)>();
     test_alignment_of<char[3], 1>();
     test_alignment_of<int, 4>();
     // The test case below is a hack. It's hard to detect what golden value
     // we should expect. In most cases it should be 8. But in i386 builds
     // with Clang >= 8 or GCC >= 8 the value is '4'.
     test_alignment_of<double, TEST_ALIGNOF(double)>();
-#if (defined(__ppc__) && !defined(__ppc64__))
-    test_alignment_of<bool, 4>();   // 32-bit PPC has four byte bool
+#if (defined(__ppc__) && !defined(__ppc64__) && !defined(_AIX))
+    test_alignment_of<bool, 4>();   // 32-bit PPC has four byte bool, except on AIX.
 #else
     test_alignment_of<bool, 1>();
 #endif
     test_alignment_of<unsigned, 4>();
 
   return 0;
 }