I have followed all the instructions.
Using a vagrant provisioned machine
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty

it all seems to work fine, but when it comes to building the bootloader the ESPIDF variable gets expanded into a path and it messes it up

LINK build/bootloader.elf
xtensa-esp32-elf-gcc: error: build/bootloader//home/vagrant/esp-idf//components/bootloader/src/main/bootloader_start.o: No such file or directory

at this point probably the ESPIDF should not be used in the path, and I think it comes from ESPCOMP in BOOTLOADER_OBJ

Can anyone help out?
I'd really like to build this, as I'm having issues with the precompiled binary's file system /flash mount.

Thanks :)