aix: disable ipv6 link local

aix does not implement ifaddrs and when retrieving the network
interfaces with uv_interface_addresses there was a test failure in
tcp_connect6_link_local.

Ref: libuv#4222 (comment)

For now disable ipv6 link local on aix to:

1) fix broken aix build
2) stop blocking libuv upgrade in node
   Ref: nodejs/node#50650

src/unix/tcp.c

@@ -30,12 +30,8 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 
-#if defined(__PASE__)
-#include <as400_protos.h>
-#define ifaddrs ifaddrs_pase
-#define getifaddrs Qp2getifaddrs
-#define freeifaddrs Qp2freeifaddrs
-#else
+// ifaddrs is not implemented on AIX
+#if !defined(_AIX)
 #include <ifaddrs.h>
 #endif
 
@@ -210,6 +206,10 @@ int uv__tcp_bind(uv_tcp_t* tcp,
 
 
 static int uv__is_ipv6_link_local(const struct sockaddr* addr) {
+// disable link local on AIX & PASE for now
+#if defined(_AIX)
+  return 0;
+#else
   const struct sockaddr_in6* a6;
   uint8_t b[2];
 
@@ -220,10 +220,15 @@ static int uv__is_ipv6_link_local(const struct sockaddr* addr) {
   memcpy(b, &a6->sin6_addr, sizeof(b));
 
   return b[0] == 0xFE && b[1] == 0x80;
+#endif
 }
 
 
 static int uv__ipv6_link_local_scope_id(void) {
+// disable link local on AIX & PASE for now
+#if defined(_AIX)
+  return 0;
+#else
   struct sockaddr_in6* a6;
   struct ifaddrs* ifa;
   struct ifaddrs* p;
@@ -245,6 +250,7 @@ static int uv__ipv6_link_local_scope_id(void) {
 
   freeifaddrs(ifa);
   return rv;
+#endif
 }