cross compile friendly cpack deb

[Aposhian]

The current CpackDebConfig.cmake.in has some restrictions that make it difficult to use in a Cross compile toolchain setup.

• It requires the lsb_release binary to be available or it fails, even though this is just used for an info log
• CPACK_DEBIAN_PACKAGE_SHLIBDEPS is forced on, even if it is turned off in the CMake cache
• CPACK_DEBIAN_PACKAGE_ARCHITECTURE is forced to be populated from dpkg --print-architecture on the compiling system.

These changes should not change behavior for anyone doing a normal packaging flow. However, they introduce additional flexibility to set CPACK_DEBIAN_PACKAGE_ARCHITECTURE and CPACK_DEBIAN_PACKAGE_SHLIBDEPS manually and have that be respected, as well as turning the fatal error when lsb_release is not present into a warning only.