[lld] [cmake] Fix -rpath-link in stand-alone build

[mgorny]

Summary

Set LLVM_LIBRARY_OUTPUT_INTDIR as expected by llvm_setup_rpath() macro
when doing stand-alone builds. This is required to pass correct
-rpath-link when linking shared libraries, and therefore ensure that
the linker can find dependency libraries correctly during the build.

[mgorny]

I've filed https://llvm.org/bugs/show_bug.cgi?id=31745 to track it for 4.0.0 backport.

[labath]

Looks reasonable, but I am somewhat reluctant to hit "approve" on lld changes.

lld/trunk/CMakeLists.txt

if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   include("${LLVM_CMAKE_PATH}/LLVMConfig.cmake")
 
   list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")
 
   set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
   include_directories("${LLVM_BINARY_DIR}/include" ${LLVM_INCLUDE_DIRS})
   link_directories(${LLVM_LIBRARY_DIRS})
 
+  set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
   set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin)
   find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
 
   include(AddLLVM)
   include(TableGen)
   include(HandleLLVMOptions)
 endif()