cannot compile openconnect 7.06

[Nikos Mavrogiannopoulos]

On Tue, 2015-03-31 at 09:27 +0200, Klaus Gast wrote:
> Hi,
> 
> I am trying to compile openconnect version 7.06 on my Synology NAS DS
> 212+
> This works fine up to version 7.04 but if I try to compile 7.06 I always
> end up with the following error:
> 
> =============================================================
> ./.libs/libopenconnect.so: undefined reference to `esp_shutdown'
> collect2: ld returned 1 exit status
> =============================================================

That is defined in esp.c which is compiled unconditionally. Could it be
some clash with some system header? Do you see some related warning
during compilation?