I followed the instructions in the cyanogenmod wiki page to build a custom ROM for grouper (Nexus 7 wifi only model). However, the CM-DATE-UNOFFICIAL.zip file is not created. I get this error message --
No private recovery resources for TARGET_DEVICE grouper.
I followed the answer in this link to add below line
TARGET_KERNEL_CONFIG := cyanogenmod_grouper_defconfig
to ~/android/system/device/asus/grouper/BoardConfig.mk and did "make modules" and "make grouper_defconfig", "make grouper" to no avail.
From further research, I found that I might be missing the kernel. I followed the android documentation on building the kernel. However, this also did not solve the issue (I might have not placed the kernel at the right location). Can someone tell me what I am missing?
I was able to generate the zip file. The main issue was that Ubuntu by default uses OpenJDK while Cyanogenmod needs Oracle JDK. Downloading and using Oracle JDK and following rest of the steps mention in this xda-developers forum thread generated the zip file. Also make sure that you have plenty of swap space (atleast as much as your ram or twice of that if possible)
Another thing that is not mentioned in the wiki for building Cyanogenmod is that the kernel has to be built first. I followed this link to build the Android kernel.