tools: add additonal include dirs for V8 on AIX

On AIX, we now include src/wasm/float16.h from within src/utils/utils.h
and src/wasm/float16.h includes additional header files.

Author: abmusse

tools/v8_gypfiles/v8.gyp

@@ -503,6 +503,9 @@
             },
           ],
         }],
+        ['OS in "aix os400"', {
+          'dependencies': ['fp16'],
+        }],
       ],
     },  # v8_snapshot
     {