Update cross script (#2686)

* Uodated cross script

* Updated cross script

* Updated cross script, added more red text and fixed patching.

* Made the number of parallel jobs a user variable

* Updated build_cross_gcc script with sha256sums and minor fixes.

* Minor updates?

* clean sha256sum and use nproc --all

* Remove 'mkdir' reference.

* Removed Cloog references.