Update .gitmodules to work for docker compiler

[Tom-evnut]

Fixes issues I was having. Compiler now does this and finishes compiling:

GIT SUBMODULE Submodule 'libopencm3' (https://www.github.com/jsphuebner/libopencm3.git) registered for path 'libopencm3' Submodule 'libopeninv' (https://www.github.com/jsphuebner/libopeninv.git) registered for path 'libopeninv' Cloning into '/app/ccs32clara/libopencm3'... warning: redirecting to https://github.com/jsphuebner/libopencm3.git/ Cloning into '/app/ccs32clara/libopeninv'... warning: redirecting to https://github.com/jsphuebner/libopeninv.git/ Submodule path 'libopencm3': checked out '3413ef88067558cba8be90be6aa339a33788f88e' Submodule path 'libopeninv': checked out '613097e26ae578b032c320970be47d3428232fbb' MAKE libopencm3 make[1]: Entering directory '/app/ccs32clara/libopencm3'

[jsphuebner]

Oh that's odd, was thinking the protocol would propagate to the sub modules. This kindof breaks it for developers because you can't push via https anymore.
Will see if there's a solution that covers both cases

[jsphuebner]

Ok, I think as I'm the only developer right now who will also push changes to libopeninv or libopencm3 I can use the "insteadOf" directive in .gitconfig. 2nd answer here: https://stackoverflow.com/questions/40841882/automatically-access-git-submodules-via-ssh-or-https

The relative path doesn't seem to work across user names (clara on uhi22 and lib.... on jsphuebner)

[jsphuebner]

Updated again.
Relative paths do work. I had just specified it incorrectly it once git submodule update is called it doesn't seem to re-read .gitmodules.