Backport 2.x: Fix test code to can be built on alpine #4969

[jclab-joseph]

Description

This is backporting for 2.x about #4969 pr.

When build via cmake on alpine linux, cause the following error: This PR fix the error.

[ 99%] Building C object tests/CMakeFiles/test_suite_net.dir/test_suite_net.c.o
In file included from .../tests/suites/test_suite_net.function:12:
/usr/include/sys/fcntl.h:1:2: error: #warning redirecting incorrect #include <sys/fcntl.h> to <fcntl.h> [-Werror=cpp]
    1 | #warning redirecting incorrect #include <sys/fcntl.h> to <fcntl.h>
      |  ^~~~~~~
cc1: all warnings being treated as errors

Status

READY

Requires Backporting

NO

Migrations

If there is any API change, what's the incentive and logic for it.

NO

Steps to test or reproduce

Before

https://github.com/jclab-joseph/mbedtls/actions/runs/1264843158

The build succeeds in ubuntu but fails in alpine.

After

https://github.com/jclab-joseph/mbedtls/actions/runs/1264845085

Both ubuntu and alpine builds succeed.

[daverodgman]

LGTM