dh_auto_install is a debhelper program that tries to automatically install built files. It does so by
running the appropriate command for the build system it detects the package uses. For example, if there's
a Makefile and it contains a install target, then this is done by running make (or MAKE, if the
environment variable is set). If there is a setup.py or Build.PL, it is used. Note that the Ant build
system does not support installation, so dh_auto_install will not install files built using Ant.
In compat 14 or later, dh_auto_install will use debian/tmp as the default --destdir and should be moved
from there to the appropriate package build directory using dh_install(1) or similar tools. Though if the
single-binary addon for dh(1) is activated, then it will pass an explicit --destdir=debian/package/ to
dh_auto_install.
For earlier compat levels then unless --destdir option is specified, the files are installed into
debian/package/ if there is only one binary package. In the multiple binary package case, the files are
instead installed into debian/tmp/, and should be moved from there to the appropriate package build
directory using dh_install(1) or similar tools.
DESTDIR is used to tell make where to install the files. If the Makefile was generated by MakeMaker from
a Makefile.PL, it will automatically set PREFIX=/usr too, since such Makefiles need that.
This is intended to work for about 90% of packages. If it doesn't work, or tries to use the wrong install
target, you're encouraged to skip using dh_auto_install at all, and just run make install manually.