[OpenMP] Adjust using the NVPTX architecture detection tool

[jhuber6]

Summary

A previous patch by @arsenm adjusted these to find the amdgpu-arch
tool correctly if we do a LLVM_ENABLE_PROJECTS build. This patch
applies the same to nvptx-arch tool to keep it consistent.

[tianshilei1992]

LG

openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake

 find_package(CUDAToolkit QUIET)
 set(LIBOMPTARGET_DEP_CUDA_FOUND ${CUDAToolkit_FOUND})
 
 ################################################################################
 # Looking for NVIDIA GPUs...
 ################################################################################
 set(LIBOMPTARGET_DEP_CUDA_ARCH "sm_35")
 
-find_program(LIBOMPTARGET_NVPTX_ARCH NAMES nvptx-arch PATHS ${LLVM_BINARY_DIR}/bin)
+if(TARGET nvptx-arch)
+  get_property(LIBOMPTARGET_NVPTX_ARCH TARGET nvptx-arch PROPERTY LOCATION)
+else()
+  find_program(LIBOMPTARGET_NVPTX_ARCH NAMES nvptx-arch
+               PATHS ${LLVM_TOOLS_BINARY_DIR}/bin)
+endif()
+
 if(LIBOMPTARGET_NVPTX_ARCH)
   execute_process(COMMAND ${LIBOMPTARGET_NVPTX_ARCH}
                   OUTPUT_VARIABLE LIBOMPTARGET_NVPTX_ARCH_OUTPUT
                   OUTPUT_STRIP_TRAILING_WHITESPACE)
   string(REPLACE "\n" ";" nvptx_arch_list "${LIBOMPTARGET_NVPTX_ARCH_OUTPUT}")
   if(nvptx_arch_list)
     set(LIBOMPTARGET_FOUND_NVIDIA_GPU TRUE)
     set(LIBOMPTARGET_NVPTX_DETECTED_ARCH_LIST "${nvptx_arch_list}")
     list(GET nvptx_arch_list 0 LIBOMPTARGET_DEP_CUDA_ARCH)
   endif()
 endif()
 
 
 ################################################################################
 # Looking for AMD GPUs...
 ################################################################################
 
 if(TARGET amdgpu-arch)
   get_property(LIBOMPTARGET_AMDGPU_ARCH TARGET amdgpu-arch PROPERTY LOCATION)
- else()
-   find_program(LIBOMPTARGET_AMDGPU_ARCH NAMES amdgpu-arch PATHS ${LLVM_BINARY_DIR}/bin)
+  find_program(LIBOMPTARGET_AMDGPU_ARCH NAMES amdgpu-arch
+               PATHS ${LLVM_TOOLS_BINARY_DIR}/bin)
 endif()
 
 if(LIBOMPTARGET_AMDGPU_ARCH)
   execute_process(COMMAND ${LIBOMPTARGET_AMDGPU_ARCH}
                   OUTPUT_VARIABLE LIBOMPTARGET_AMDGPU_ARCH_OUTPUT
                   OUTPUT_STRIP_TRAILING_WHITESPACE)
   string(REPLACE "\n" ";" amdgpu_arch_list "${LIBOMPTARGET_AMDGPU_ARCH_OUTPUT}")
   if(amdgpu_arch_list)