tests/c_lib: Don't assume a particular PRNG from Picolibc [v2]
tests/c_lib: Don't assume a particular PRNG from Picolibc [v2]

The random/rand tests assume the PRNG operates in a specific fashion,
which is not true when running Picolibc.

v2:
	Call ztest_test_skip for picolibc

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

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