[libclc] [libclc] Change libclc install dir to ${clang_resource_dir}/lib/libclc in in-tree build (PR #163896)

[Wenju He via cfe-commits]

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@@ -100,10 +101,12 @@ else()
   # Setup the paths where libclc runtimes should be stored. By default, in an
   # in-tree build we place the libraries in clang's resource driectory.
   include(GetClangResourceDir)
-  get_clang_resource_dir( LIBCLC_OUTPUT_DIR PREFIX ${LLVM_LIBRARY_OUTPUT_INTDIR}/.. )
+  get_clang_resource_dir( LIBCLC_INSTALL_DIR )
 
   # Note we do not adhere to LLVM_ENABLE_PER_TARGET_RUNTIME_DIR.
-  set( LIBCLC_OUTPUT_LIBRARY_DIR ${LIBCLC_OUTPUT_DIR}/lib/libclc )
+  cmake_path( APPEND LIBCLC_INSTALL_DIR "lib" "libclc" )
+  cmake_path( GET LLVM_LIBRARY_OUTPUT_INTDIR PARENT_PATH LIBCLC_OUTPUT_LIBRARY_DIR )
+  cmake_path( APPEND LIBCLC_OUTPUT_LIBRARY_DIR ${LIBCLC_INSTALL_DIR} )
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wenju-he wrote:

> Appending an (likely) absolute path ${LIBCLC_INSTALL_DIR}

not true, get_clang_resource_dir always returns a relative path

https://github.com/llvm/llvm-project/pull/163896