[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

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;
 }