rust-cross-canadian: Fix for the issue caused by using sdk shell

rust-cross-canadian: Fix for the issue caused by using sdk shell

This is a fix for the fix in YOCTO #14878. When the shebang is more than
128 characters the default shell /bin/sh is used instead of SDK shell as
a fallback, which causes problems with LD_LIBRARY_PATH. With this patch
shell usage is avoided as we use a C wrapper and unset LD_LIBRARY_PATH
that way.

[YOCTO #14892]

Signed-off-by: Sundeep KOKKONDA <sundeep.kokkonda@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>