Use relative rpath so that the installation and build dirs are reloca…

…table.

This works by asking cmake to use the "install rpath", but setting that rpath
to be relative.

Thanks a lot to Brad King for the help with CMake!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201921 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -423,9 +423,13 @@ set( CMAKE_RUNTIME_OUTPUT_DIRECTORY ${LLVM_BINARY_DIR}/bin )
 set( CMAKE_LIBRARY_OUTPUT_DIRECTORY ${LLVM_BINARY_DIR}/lib )
 set( CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LLVM_BINARY_DIR}/lib )
 
-if( NOT DEFINED CMAKE_INSTALL_RPATH )
-  set( CMAKE_INSTALL_RPATH "\$ORIGIN/../lib")
-endif( NOT DEFINED CMAKE_INSTALL_RPATH )
+set(CMAKE_BUILD_WITH_INSTALL_RPATH ON)
+if (APPLE)
+  set(CMAKE_INSTALL_NAME_DIR "@rpath")
+  set(CMAKE_INSTALL_RPATH "@executable_path/../lib")
+else(UNIX)
+  set(CMAKE_INSTALL_RPATH "\$ORIGIN/../lib")
+endif()
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)