utils/genrandconfig: add ubi handling

Add a custom case to make sure that a random configuration with an empty
configuration file for ubi doesn't fail.

ubinize: error!: no sections found the ini-file "/home/buildroot/autobuild/instance-2/output-1/build/ubinize.cfg"

Fixes:
 - http://autobuild.buildroot.org/results/f678c17cc4df06fb2737467e769cd8f72a3ea420

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

utils/genrandconfig

@@ -526,6 +526,12 @@ def fixup_config(sysinfo, configfile):
         configlines.remove('BR2_TARGET_ROOTFS_UBIFS_MAXLEBCNT=2048\n')
         configlines.append('BR2_TARGET_ROOTFS_UBIFS_MAXLEBCNT=41610\n')
 
+    if 'BR2_TARGET_ROOTFS_UBI=y\n' in configlines and \
+       'BR2_TARGET_ROOTFS_UBI_USE_CUSTOM_CONFIG=y\n' in configlines and \
+       'BR2_TARGET_ROOTFS_UBI_CUSTOM_CONFIG_FILE=""\n' in configlines:
+        configlines.remove('BR2_TARGET_ROOTFS_UBI_USE_CUSTOM_CONFIG=y\n')
+        configlines.remove('BR2_TARGET_ROOTFS_UBI_CUSTOM_CONFIG_FILE=""\n')
+
     if 'BR2_TARGET_S500_BOOTLOADER=y\n' in configlines and \
        'BR2_TARGET_S500_BOOTLOADER_BOARD=""\n' in configlines:
         configlines.remove('BR2_TARGET_S500_BOOTLOADER=y\n')