utils/genrandconfig: add missing new line when creating the configuration

When adding the custom BR2_WGET value in the configuration,
genrandconfig forgets to add a newline. Due to this, the next option
that is added is printed on the same line as BR2_WGET="", which causes
it to be ignored.

Due to this, in all builds, the line right after BR2_WGET was
ignored. It could have been BR2_ENABLE_DEBUG, BR2_INIT_BUSYBOX,
BR2_INIT_SYSTEMD, BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV,
BR2_STATIC_LIBS or BR2_PACKAGE_PYTHON_PY_ONLY depending on the
randomization.

Fix that by adding a proper newline at the end of the BR2_WGET option.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>