Boolean toggle to make CPack use DESTDIR mechanism when packaging.

DESTDIR means DESTination DIRectory. It is commonly used by makefile users in order to install software at non-default location. It is a basic relocation mechanism that should not be used on Windows (see CMAKE_INSTALL_PREFIX documentation). It is usually invoked like this:

make DESTDIR=/home/john install

which will install the concerned software using the installation prefix, e.g. /usr/local prepended with the DESTDIR value which finally gives /home/john/usr/local. When preparing a package, CPack first installs the items to be packaged in a local (to the build tree) directory by using the same DESTDIR mechanism. Nevertheless, if CPACK_SET_DESTDIR is set then CPack will set DESTDIR before doing the local install. The most noticeable difference is that without CPACK_SET_DESTDIR, CPack uses CPACK_PACKAGING_INSTALL_PREFIX as a prefix whereas with CPACK_SET_DESTDIR set, CPack will use CMAKE_INSTALL_PREFIX as a prefix.

Manually setting CPACK_SET_DESTDIR may help (or simply be necessary) if some install rules uses absolute DESTINATION (see CMake install() command). However, starting with CPack/CMake 2.8.3 RPM and DEB installers tries to handle DESTDIR automatically so that it is seldom necessary for the user to set it.