build: add /opt/freeware/... to AIX library path

To ease the use of the AIX binaries, add
/opt/freeware/lib/pthread{/ppc64} into the search path encoded into the
library, so that any version the user has installed from the common download
locations will work out of the box without having to explicitly set LIBPATH
in their environment.

node.gyp

@@ -936,6 +936,16 @@
             }, {
               'type': 'executable',
             }],
+            ['target_arch=="ppc64"', {
+              'ldflags': [
+                '-Wl,-blibpath:/usr/lib:/lib:/opt/freeware/lib/pthread/ppc64'
+              ],
+            }],
+            ['target_arch=="ppc"', {
+              'ldflags': [
+                '-Wl,-blibpath:/usr/lib:/lib:/opt/freeware/lib/pthread'
+              ],
+            }]
           ],
           'dependencies': ['<(node_core_target_name)', 'node_exp'],