linking arm libc instead of thumb

Hi,

Sorry, I must be doing something wrong, but I can't seem to find what.
I am using Ubuntu 18.04 arm-none-eabi-gcc (15:6.3.1+svn253039-1build1) 6.3.1 20170620 and it looks like the selected libc is the ARM one, not the THUMB one. I first detected this through a BUS FAULT which upon investigation and disassembly (the .lss file) looks like ARM code. Moreover I tried the following commands:

> arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 --print-file-name=libc.a
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a
^^^ I have seen in another post that when some guy types the same command line (although for a Cortex-M4), he gets 'thumb' somewhere in the returned path.

> arm-none-eabi-gcc -mthumb -mcpu=cortex-m3 --print-multi-directory
thumb/v7-m

Other libs (for example function __eabi__uidiv) look like thumb code.

> lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic

Thank you for your time,
Best regards,
Jérôme.