Thank you for the explanations as always. It’s a great help. I have the crt* files and libpthread files, the problem was compiler not finding them. I thing the error came at the linking stage.
However, I gave up on that and started cross compiling ROS fully and ended up creating this fork of an old repository which was for crosscompiling an older ROS version.
Later I found out that there already is a repo which does what I want (I don’t know how I missed that). It cross compiles your ROS packages with no hassle.
https://github.com/ros-tooling/cross_compile
If no other problems arise from my dependencies, I’ll be using this from here onward