Replace deprecated CUDA_TOOLKIT_ROOT_DIR with CUDAToolkit_ROOT (#213)

LLVM does not use CUDA_TOOLKIT_ROOT_DIR anymore after
llvm/llvm-project@3de162f.
Instead use `CUDAToolkit_ROOT` to let CMake search for CUDA.

Author: Meinersbur

buildbot/osuosl/master/config/builders.py

@@ -1755,7 +1755,7 @@
                         clean=True,
                         enable_runtimes=['offload'],
                         extraCmakeArgs=[
-                                "-DCUDA_TOOLKIT_ROOT_DIR=/opt/cuda",
+                                "-DCUDAToolkit_ROOT=/opt/cuda",
                                 "-DCLANG_ENABLE_STATIC_ANALYZER=OFF",
                                 "-DCLANG_ENABLE_ARCMT=OFF",
                                 "-DCLANG_ENABLE_OBJC_REWRITER=OFF",
@@ -1787,7 +1787,7 @@
                         clean=True,
                         enable_runtimes=['openmp', 'offload'],
                         extraCmakeArgs=[
-                                "-DCUDA_TOOLKIT_ROOT_DIR=/opt/cuda",
+                                "-DCUDAToolkit_ROOT=/opt/cuda",
                                 "-DCLANG_ENABLE_STATIC_ANALYZER=OFF",
                                 "-DCLANG_ENABLE_ARCMT=OFF",
                                 "-DCLANG_ENABLE_OBJC_REWRITER=OFF",