Removed precarious cross compile shell script.

Removed precarious cross compile shell script.

CMake provides a standardized way to cross compile packages by
using -DCMAKE_TOOLCHAIN_FILE at configure time.

Also recent distributions like opensuse provides up to date native mingw
binary packages and cross compile packages which reduces the cross
compile setup to package installation and setup of a cross tool chain file
as documented at http://www.vtk.org/Wiki/CMake_Cross_Compiling.

https://bugs.freedesktop.org/show_bug.cgi?id=59733
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>