cmake: GNUInstallDirs for Debian cross-builds
cmake: GNUInstallDirs for Debian cross-builds

Simply including this module means that the `dh` environment understands
what a cross build means.

fanchanghu/sysrepo,rastislavszabo/sysrepo,rastislavszabo/sysrepo,morganzhh/sysrepo,morganzhh/sysrepo,rastislavszabo/sysrepo,lukasmacko/sysrepo,lukasmacko/sysrepo,lukasmacko/sysrepo,lukasmacko/sysrepo,morganzhh/sysrepo,rastislavszabo/sysrepo,rastislavszabo/sysrepo,rastislavszabo/sysrepo,fanchanghu/sysrepo,lukasmacko/sysrepo,morganzhh/sysrepo,fanchanghu/sysrepo,morganzhh/sysrepo,fanchanghu/sysrepo,morganzhh/sysrepo,rastislavszabo/sysrepo,lukasmacko/sysrepo,fanchanghu/sysrepo,fanchanghu/sysrepo,lukasmacko/sysrepo,fanchanghu/sysrepo,morganzhh/sysrepo