No /system/build.prop in Nexus 7 (2012 / Wi-Fi) + Android Lollipop 5.1.1 after fresh installation

Question

I've just updated my [old] Nexus 7 (2012 / Wi-Fi) to Android Lollipop 5.1.1 following the "standard" procedure I've alway gone through since I've owned it;

Here's what I've done so far:

1. Booted into the bootloader
2. Unlocked the bootloader via fastboot
3. Flashed everything via fastboot using a custom bash script

#!/bin/bash
fastboot flash bootloader bootloader-grouper-4.23.img
fastboot reboot-bootloader
sleep 5
fastboot flash recovery recovery-clockwork-6.0.4.3-grouper.img
fastboot flash boot boot.img
fastboot flash system system.img
fastboot flash userdata userdata.img

_{*This did nothing more than flashing the stock Android Lollipop 5.1.1 (LMY47V) (nakasi) firmware for Nexus 7 (2012 / Wi-Fi) images downloaded from Google Developers, aside from the recovery image, which was the ClockworkMod Recovery 6.0.4.3 image instead.}

4. Booted straight into the recovery mode
5. Downloaded and pushed SuperSU using adb push UPDATE-SuperSU-v2.46.zip /mnt/sdcard/0/
6. Installed SuperSU via the recovery mode

And here is where I got stuck. The idea was to edit /system/build.prop in order to force the first setup to allow me to skip the Wi-Fi connection step, however apparently there's no /system/build.prop whatsoever in the system.

Here's what I tried through the adb shell (as root):

user@debian:~$ adb pull /system/build.prop .
remote object '/system/build.prop' does not exist
user@debian:~$ adb shell
~ # ls -la /system/
__bionic_open_tzdata: couldn't find any tzdata when looking for localtime!
__bionic_open_tzdata: couldn't find any tzdata when looking for GMT!
__bionic_open_tzdata: couldn't find any tzdata when looking for posixrules!
drwxr-xr-x    3 root     root             0 Jan  1  1970 .
drwxr-xr-x   22 root     root             0 Jul 23 07:40 ..
drwxr-xr-x    2 root     root             0 Jan  1  1970 bin
~ # find / -type f -name 'build.prop'
~ # exit

Answer 1

The /system partition wasn't mounted; I've noticed this only manually browsing the /system/bin/ folder, which was empty.

I mounted the partition within the recovery mode by browsing to "mounts and storage" and by selecting "mount /system"; afterwards I've been able to run adb pull /system/build.prop ., edit the file and upload it again running adb push build.prop /system/build.prop.

To unmount the partition afterwards, one might browse to "mounts and storage" and select "unmount /system".