[CMake] padding link arguments to the linker

[Brad King]

Mike Jackson wrote:
> So if I turn on RPATH, and rpath uses -install_name, where do I  
> actually specify the RPATH to use? or can I specify the path at all?

Enabling VTK_USE_RPATH is intended for developers to be able to run VTK 
programs from the build tree without installing or setting any 
environment variables.  It always sets the install_name to point to the 
full path to each library in the build tree.  This is why installation 
is disabled.

CMake does not currently support a user-configured rpath or 
install_name.  If CMAKE_SKIP_RPATH is ON then no rpath is generated and 
install_name is set to the name of the library.  If CMAKE_SKIP_RPATH is 
OFF then rpath and install_name both point to the build tree locations.

CMake support for specifying an rpath/install-name is planned but has 
not yet been implemented.

If you intend to just distribute a binary for your application then you 
can work around this limitation as follows.  First build VTK with 
VTK_USE_RPATH set to ON.  Use a build tree with a really long name. 
Then build your application against the VTK build tree.  Copy the 
libraries to your application tree and use install_name_tool to change 
the install_name.  There will easily be enough room allocated because of 
the long build tree name.

-Brad