I tried switching a buildroot based CI server to the 26.04

One Makefile statement triggered a bug in rust ln:

  src/%:
      @ln -sfn $(DIR)/foo src

In parallel build, we would get random failure:

  ln: Already exists

Rewrote that Makefile to work-around it, and ended up with the same kind of bugs with parallel $(INSTALL) -D ...

Tried latest ubuntu 26.10 which supposedly fixes a lot of TOCTOU races in rust coreutils, but no better.

Gave up and switched back to original coreutils.