Libraries (such as 'libtorch_cpu.so') and executables (such as
'torch_shm_manager') get installed, quite surprisingly, to
'lib/pythonX.Y/site-packages/{bin,lib}'.  Make sure RUNPATH matches that.

diff --git a/cmake/Dependencies.cmake b/cmake/Dependencies.cmake
index be45936a8..7b19e5359 100644
--- a/cmake/Dependencies.cmake
+++ b/cmake/Dependencies.cmake
@@ -4,7 +4,7 @@ if(APPLE)
   set(CMAKE_MACOSX_RPATH ON)
   set(_rpath_portable_origin "@loader_path")
 else()
-  set(_rpath_portable_origin $ORIGIN)
+  set(_rpath_portable_origin $ORIGIN/../lib)
 endif(APPLE)
 # Use separate rpaths during build and install phases
 set(CMAKE_SKIP_BUILD_RPATH  FALSE)