The use of include_directories and link_directories pollutes global include and link directories. This change adds IMPORTED targets using the external projects and then links the funchook targets against them.
This also avoids issues seen where captone fails to be found at link time "error: ld returned 1 exit status cannot find -lcapstone" when making use of certain toolchain files.

INTERFACE_INCLUDE_DIRECTORIES does not allow non-existent directories so ensure the directory is valid using file(MAKE_DIRECTORY). See  https://gitlab.kitware.com/cmake/cmake/-/issues/15052 for details.

The capstone target was previously being setup using ExternalProject_Get_Property however installing the external project and using the generic include/lib directories solves issues with config based generators.

GNUInstallDirs may not always output to lib and may instead output to lib or lib64 or lib/<multiarch-tuple> on Debian.

Avoid "Unable to determine default CMAKE_INSTALL_LIBDIR directory because no target architecture is known.  Please enable at least one language before including GNUInstallDirs."

Tag 3.1.0 of Zydis includes GNUInstallDirs prior to a language being enabled meaning its CMAKE_INSTALL_LIBDIR will always result in lib rather than its correct lib/lib64 variant. Note that Zydis master branch has fixed this issue.