gdb-cross-canadian: Fix linking issues when python support is enabled

gdb-cross-canadian: Fix linking issues when python support is enabled

gdb-cross-canadian was linking with static version of libpython
and looking for build host python when run. This could be mismatch
between python-nativesdk and build host provided python. So we
make it consistent to always use python-nativesdk

Instead of adding bunch of -L we add -rpath and -rpath-link
so that gdb finds all needed libraries in SDK and does not
reach out into host

This should fix yocto PR# 2077 as well.

(From OE-Core rev: d56177c59b5e237a501281d806724885456f0193)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>