Not running on RPi B3+ with Ubuntu Bionic

[buildingautomator]

After patching gold-threads.cc line 288, I was able to build the complete toolchain.
I checked everything including the file format which my Mac with Mojave said was:

"ELF 64-bit LSB pie executable ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, for GNU/Linux 3.7.0, with debug_info, not stripped"

Copied it to an RPi 3B+ with Ubuntu Bionic but ./helloworld would not start with bash error:
"./helloworld: cannot execute binary file: Exec format error"

Any idea why that might be the case ?
(RPi running Linux 4.14.34-hypriotos-v7+ armv71 GNU/Linux)