Instead use qmake IDE_LIBRARY_BASENAME=lib64 to set it to lib64.

This is helpfull for building plugins from outside
the QtCreator source tree.

use the data copying custom compiler approach here, too.
this leaves more work to qmake, which is good.
on the upside, pluginspecs will be installed when they change without
having force a re-link of the plugin itself.
on the downside, installation of a pluginspec will force a re-link of
the plugin. oh, well - you can't have it all (with qmake) ...

IDE_LIBEXEC_PATH is still the bindir, so it's kinda fake. oh, well.

now bin and share are not pegged to linking the executable any more,
but are proper subdirs targets of their own.
unforturnately, qmake is a bit tenacious, so we hack around a bit. :)

more or less in passing by, i removed some superfluous trailing slashes
and added path normalization as well.

Reviewed-by: hjk

Details:  LD_LIBRARY_PATH setting still missing

Details:  Creator on Linux works now in two modes:
          1) out of the build dir (shadow builds to be tested)
          2) make INSTALL_ROOT=/prefix install

Details:  Make install works now, we just have to agree on layout
details and check for mac compatibility.

Also, plugins will carry no version in their filename anymore starting with
this commit. Versioning happens in the creators pluginloader using the pluginspec file.

Fixed the build system. Generate the object files for release and debug builds in different directories.