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

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

Differential Revision: https://reviews.llvm.org/D112087

Author: mandlebug

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

@@ -6,9 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// Fails for 32-bit builds on AIX.
-// UNSUPPORTED: LIBCXX-AIX-FIXME
-
 // type_traits
 
 // alignment_of
@@ -54,8 +51,8 @@ int main(int, char**)
     // 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