compiling native_posix64 with unistd.h & net/net_ip.h fail

[ehudmarvell]

posix64 comilation fail on:

/usr/include/unistd.h:277:21: error: conflicting types for ‘socklen_t’
typedef __socklen_t socklen_t;
^~~~~~~~~
In file included from ../src/main.c:9:0:
/home/ehudn/work/new_zephyr/zephyr/include/net/net_ip.h:154:16: note: previous declaration of ‘socklen_t’ was here
typedef size_t socklen_t;
^~~~~~~~~

To Reproduce
1.
add to helloworld app the following lines

#include <net/net_ip.h>
#include <unistd.h>

2. cd samples/hello_world/
3. mkdir build
4. cd build
5. cmake -GNinja -DBOARD=native_posix64 ..
6. use the attaching config
   config.txt
7. ninja
8. See error

Expected behavior
compilation pass

Environment:

• OS: LINUX
• Toolchain Zephyr SDK
• Commit SHA: a4f4f6d

[pfalcon]

native_posix* targets: a) leak host headers into the build; b) not compatible with Zephyr POSIX subsystem (because there's no proper separation between host vs Zephyr POSIX layers). This is known problem, see e.g. #13054

Unassigning from myself and assigning to @aescolar. I'd also suggest to lower priority of this (because this is effectively a known limitation of native_posix* targets).

[aescolar]

@ehudmarvell This is a not a bug as such, as much as something that was willingly chosen to stop supporting :( . You can see some history in #13054. You can also see #13540 where the POSIX API shim was disabled in native_posix targets.
I will be closing this ticket as you are trying to do something which is just not supported. If you would like this to be supported you could either create a "feature request", or chip-in in #13540