I am not sure about the Torizon Core Builder but I was facing the same issue while compiling Yocto using Bitbake based on BSP 5.7.2.
I have added these lines to the conf/local.conf file and it solved the problem:
MIRRORS += " \
git://source.codeaurora.org/external/imx/ git://github.com/nxp-imx/;protocol=https \n \
https://source.codeaurora.org/external/imx/ https://github.com/nxp-imx/ \n \
http://source.codeaurora.org/external/imx/ http://github.com/nxp-imx/ \n \
gitsm://source.codeaurora.org/external/imx/ gitsm://github.com/nxp-imx/;protocol=https \n \
"
Hope it works for you, too.
Regards,
Aditya