cygwin issue

I'm trying to compile a simple program under cygwin. the source code 
only contain the libnet_init fuction. the problem is at linking time.
it seems that it cannot resolve the errno variable even if it is defined 
in libc.a

anyone with the same problem ?

gcc zz.c -o zz -lnet -lwpcap -liphlpapi -lws2_32 -lpacket

/libnet.a(libnet_init.o)(.text+0x105): In function `libnet_init':
/libnet_init.c:69: undefined reference to `__errno'
/libnet.a(libnet_pblock.o)(.text+0x179): In function `libnet_pblock
_probe':
/libnet_pblock.c:93: undefined reference to `__errno'
/libnet.a(libnet_pblock.o)(.text+0x39a): In function `libnet_pblock
_new':/libnet_pblock.c:162: undefined reference to `__errno'
/libnet.a(libnet_pblock.o)(.text+0x857): In function `libnet_pblock
_coalesce':
/libnet_pblock.c:314: undefined reference to `__errno'
/libnet.a(libnet_link_win32.o)(.text+0x916): In function `libnet_wi
n32_read_arp_table':
/libnet_link_win32.c:309: undefined reference to `__assert'
/libnet.a(libnet_resolve.o)(.text+0x2ac): In function `libnet_name2
addr4':
/libnet_resolve.c:128: undefined reference to `__errno'
collect2: ld returned 1 exit status


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