Don't use readlink to get dirname of install dir
Don't use readlink to get dirname of install dir

If you use the path to the install directory (which seems the "normal" way of
doing things) then the readlink will return nothing and dirname will fail...

Signed-off-by: Dirk Hohndel <a00b27378a09822d5638cdfb8c2e7ccc36d74c56@hohndel.org>

jmara/yoursway-create-dmg,digitalreasoning/create-dmg,strukturag/create-dmg,andreyvit/create-dmg,jmara/yoursway-create-dmg,heavilessrose/create-dmg,digitalreasoning/create-dmg,heavilessrose/create-dmg,mrpau/create-dmg,jmara/yoursway-create-dmg,strukturag/create-dmg,andreyvit/create-dmg,mrpau/create-dmg,andrey-str/create-dmg,andrey-str/create-dmg,andrey-str/create-dmg,mrpau/create-dmg,andreyvit/create-dmg,digitalreasoning/create-dmg,heavilessrose/create-dmg,strukturag/create-dmg