tests: ztest: Use #if defined()

This compile test should be checking if a symbol has been defined,
otherwise it is using the kconfig value directly.  This fixes a warning

../src/main.c:115:37: warning: "CONFIG_SOC_QEMU_ARC" is not defined,
evaluates to 0 [-Wundef]

when using the -Wundef flag.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>