[fedora-arm] How do I enable mounting /usr as a separate (read-only) partition on Fedora 17?

[Alex Villací­s Lasso]

I have this ARM project for which I have installed Fedora 17 armv5tel on a SD card. The installation is one small FAT partition where the kernel and initramfs files can be placed, and one EXT3 partition where the root filesystem lives. This mode of 
operation boots correctly.

Now I want to move the contents of /usr to a separate partition, and lock this partition read-only. After some investigation on how to coax the bootloader to load the initramfs, I managed to boot the kernel with the initramfs, only to find out that it 
wants to run /sbin/init . The /sbin is a symlink that should end up in /usr, but I specify the root filesystem as the rootfs in the kernel commandline, and the initramfs has not mounted /usr to resolve all of the symlinks, even after specifying the device 
in /etc/fstab. After some googling, it seems that the /usr separation was not fully implemented in Fedora 17, but was completed in Fedora 18.

What do I have to do to enable the /usr separation in Fedora 17? I do not really want to port the entire project to Fedora 18, and I think it will be easier to just grab the relevant packages or patches from Fedora 18, recompile for Fedora 17, install, and 
then separate the filesystem as indicated. Is this doable? What packages should I pick from Fedora 18? I know that Fedora 17 is EOL, and I do not expect any updated packages for this, but I can recompile packages.