[llvm] r201921 - Use relative rpath so that the installation and build dirs are relocatable.

[Rafael Espíndola]

> Hi Raphael,
>
> this one broke the polly build, because the libraries we are linking (libisl
> and libcloog) are not anymore in the rpath (and they are also not in the
> LD_LIBRARY_PATH). Is this change intended? Do you have an idea how to
> proceed? Is this a problem with your change, should I fix the Polly cmake or
> should we now always put such libraries into the LD_LIBRARY_PATH? (changing
> the buildbots may take a little).

It is this one:
http://lab.llvm.org:8011/builders/polly-amd64-linux/builds/15464/steps/test_polly/logs/stdio,
right?

Was the rpath of LLVMPolly.so being set in some way? What was it? My
understanding is that cmake was always setting it to the absolute path
before, which looks to be
/home/grosser/buildslave/polly-amd64-linux/llvm.obj/lib/. Now it
should be $ORIGIN/../lib, which should be the same directory.

Where is libisl.so.10?

Does it work when building with configure? What is the rpath you get
in LLVMPolly.so?

Cheers,
Rafael