[gdb/record] Handle statx system call

When running test-case gdb.reverse/fstatat-reverse.exp with target board
unix/-m32 on openSUSE Tumbleweed, I run into:
...
(gdb) PASS: gdb.reverse/fstatat-reverse.exp: set breakpoint at marker2
continue^M
Continuing.^M
Process record and replay target doesn't support syscall number 383^M
Process record: failed to record execution log.^M
^M
Program stopped.^M
0xf7fc5555 in __kernel_vsyscall ()^M
(gdb) FAIL: gdb.reverse/fstatat-reverse.exp: continue to breakpoint: marker2
...

The problems is that while with native we're trying to record these syscalls
(showing strace output):
...
openat(AT_FDCWD, "/", O_RDONLY|O_PATH)  = 3
newfstatat(3, ".", {st_mode=S_IFDIR|0755, st_size=146, ...}, 0) = 0
...
with unix/-m32 we have instead:
...
openat(AT_FDCWD, "/", O_RDONLY|O_PATH)  = 3
statx(3, ".", AT_STATX_SYNC_AS_STAT|AT_NO_AUTOMOUNT, STATX_BASIC_STATS, \
  {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=STATX_ATTR_MOUNT_ROOT, \
  stx_mode=S_IFDIR|0755, stx_size=146, ...}) = 0
...
and statx is not supported.

Fix this by adding support for recording syscall statx.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28461

gdb/linux-record.c

@@ -1046,6 +1046,12 @@ Do you want to stop the program?"),
 	return -1;
       break;
 
+    case gdb_sys_statx:
+      regcache_raw_read_unsigned (regcache, tdep->arg5, &tmpulongest);
+      if (record_full_arch_list_add_mem ((CORE_ADDR) tmpulongest, 256))
+	return -1;
+      break;
+
     case gdb_sys_uname:
       if (record_mem_at_reg (regcache, tdep->arg1,
 			     tdep->size_old_utsname))

gdb/linux-record.h

@@ -510,6 +510,7 @@ enum gdb_syscall {
   gdb_sys_dup3 = 330,
   gdb_sys_pipe2 = 331,
   gdb_sys_inotify_init1 = 332,
+  gdb_sys_statx = 383,
   gdb_sys_socket = 500,
   gdb_sys_connect = 501,
   gdb_sys_accept = 502,