* it was done with CFLAGS only in python3-maturin but it could be useful
for other recipes as well, move it to bbclass which sets CARGO_HOME
* python3-maturin buildflags issue is reproducible with scarthgap:
WARNING: python3-maturin-1.4.0-r0 do_package_qa: QA Issue: File /usr/bin/.debug/maturin in package python3-maturin-dbg contains reference to TMPDIR [buildpaths]
but not with whinlatter