To build source-based kernel:

1. Set CROSS_COMPILE to an appropriate path prefix, e.g.,

   export CROSS_COMPILE=../../cm/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin/arm-eabi-

2. Build kernel and modules:

   cd kernel; make u1_na_spr_defconfig && make -j 4 &&
      make INSTALL_MOD_PATH=.. INSTALL_MOD_STRIP=1 modules_install; cd ..

3. Copy newly-built modules to initramfs:

   find lib/modules -name '*.ko' -exec cp -a {} initramfs/lib/modules \;

4. Remove .empty files from initramfs:

   find initramfs -name '.empty' -exec rm {} +

5. Rebuild final zImage with updated initramfs:

   cd kernel; make zImage; cd ..

The completed kernel is located at kernel/arch/arm/boot/zImage.