Please support DESTDIR in Makefile

[ryandesign]

Please support the standard DESTDIR variable in your Makefile.

If I run

sudo make install DESTDIR=/tmp/root

then I would expect the files to get installed in

/tmp/root/usr/local/bin/searchfs
/tmp/root/usr/local/share/man/man1/searchfs.1

Note that your existing Makefile variable DEST_DIR, which serves an unrelated purpose, then becomes confusing. You may wish to rename that variable.