[libclc] Fix LIBCLC_OUTPUT_LIBRARY_DIR when find_package(LLVM) fails (#201816)

If we configure llvm from llvm-project/build folder, find_package(LLVM)
succeeds, `LLVM_LIBRARY_OUTPUT_INTDIR` is `build/./lib` and
`LLVM_BINARY_DIR` is `build`.

However, in #201773, find_package(LLVM) fails due to
LLVM_LIBDIR_SUFFIX=64, LLVM_LIBRARY_OUTPUT_INTDIR is
`redhat-linux-build/runtimes/runtimes-nvptx64-nvidia-cuda-bins/lib64`
and LLVM_BINARY_DIR is `redhat-linux-build`.

Use LLVM_BINARY_DIR, which is stable for both cases, for libclc output dir.

Fixes #201773

GitOrigin-RevId: 517a0755f5d128d950fc8a08b2bd45e629e40a95

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94ec63c..bc36246 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -83,9 +83,9 @@
   include(GetClangResourceDir)
   get_clang_resource_dir( LIBCLC_INSTALL_DIR )
   cmake_path( APPEND LIBCLC_INSTALL_DIR "lib" )
-
-  cmake_path( GET LLVM_LIBRARY_OUTPUT_INTDIR PARENT_PATH LIBCLC_OUTPUT_LIBRARY_DIR )
-  cmake_path( APPEND LIBCLC_OUTPUT_LIBRARY_DIR ${LIBCLC_INSTALL_DIR} )
+  cmake_path( APPEND LLVM_BINARY_DIR ${LIBCLC_INSTALL_DIR}
+    OUTPUT_VARIABLE LIBCLC_OUTPUT_LIBRARY_DIR
+  )
 endif()
 
 if( NOT LIBCLC_USE_SPIRV_BACKEND )