libc/picolibc: Set __LINUX_ERRNO_EXTENSIONS__ for picolibc
libc/picolibc: Set __LINUX_ERRNO_EXTENSIONS__ for picolibc

This makes sure extra errno values from Linux that Zephyr uses are
available.

Signed-off-by: Keith Packard <fd7f967895e9f35e58ec8a62a847a54d7fa7275f@keithp.com>

zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr