Fix 'nvc++ -stdpar'

NVC++ stdpar mode enables CUDA support but does not define the macro
`__CUDACC__`.  Any code in CCCL (which is used by NVC++ stdpar under the
covers) needs to check for either `__CUDACC__` or `_NVHPC_CUDA` being
set.

NVIDIA#1199 only checks for `__CUDACC__`
when defining `_CCCL_HOST` and `_CCCL_DEVICE` and some other macros.
This change completely broke `nvc++ -stdpar` because all functions
became unannotated host functions.

Fix this by changing several files in
libcudacxx/include/cuda/std/detail/libcxx/include to check for either
`__CUDACC__` or `_NVHPC_CUDA`.

libcudacxx/include/cuda/std/detail/libcxx/include/__cccl/execution_space.h

@@ -11,17 +11,17 @@
 #ifndef __CCCL_EXECUTION_SPACE_H
 #define __CCCL_EXECUTION_SPACE_H
 
-#ifdef __CUDACC__
+#if defined(__CUDACC__) || defined(_NVHPC_CUDA)
 #  define _CCCL_HOST         __host__
 #  define _CCCL_DEVICE       __device__
 #  define _CCCL_HOST_DEVICE  __host__ __device__
 #  define _CCCL_FORCEINLINE __forceinline__
-#else // ^^^ __CUDACC__ ^^^ / vvv !__CUDACC__
+#else // ^^^ __CUDACC__ || _NVHPC_CUDA ^^^ / vvv !__CUDACC__ && !_NVHPC_CUDA
 #  define _CCCL_HOST
 #  define _CCCL_DEVICE
 #  define _CCCL_HOST_DEVICE
 #  define _CCCL_FORCEINLINE
-#endif // !__CUDACC__
+#endif // !__CUDACC__ && !_NVHPC_CUDA
 
 #if !defined(_CCCL_EXEC_CHECK_DISABLE)
 #  if defined(_CCCL_COMPILER_NVRTC) || defined(_CCCL_CUDA_COMPILER_NVHPC) || defined(_CCCL_CUDA_COMPILER_CLANG)

libcudacxx/include/cuda/std/detail/libcxx/include/__cccl_config

@@ -131,7 +131,7 @@
 #endif // !_CCCL_COMPILER_CLANG && !_CCCL_COMPILER_GCC
 
 // Enable us to selectively silence cuda compiler warnings
-#if defined(__CUDACC__)
+#if defined(__CUDACC__) || defined(_NVHPC_CUDA)
 #  if !defined(_CCCL_CUDA_COMPILER_CLANG)
 #    define _CCCL_NV_DIAG_SUPPRESS(_WARNING)
 #    define _CCCL_NV_DIAG_DEFAULT(_WARNING)
@@ -160,7 +160,7 @@
 #      define _CCCL_NV_DIAG_DEFAULT(_WARNING)  _Pragma(_CCCL_TOSTRING(diag_default _WARNING))
 #    endif // !_CCCL_COMPILER_MSVC
 #  endif // !__NVCC_DIAG_PRAGMA_SUPPORT__
-#else // ^^^ __CUDACC__ ^^^ / vvv !__CUDACC__ vvv
+#else // ^^^ __CUDACC__ || _NVHPC_CUDA ^^^ / vvv !__CUDACC__ && !_NVHPC_CUDA vvv
 #  define _CCCL_NV_DIAG_SUPPRESS(_WARNING)
 #  define _CCCL_NV_DIAG_DEFAULT(_WARNING)
 #endif // other compilers

libcudacxx/include/cuda/std/detail/libcxx/include/__config

@@ -61,7 +61,7 @@
 #  define _LIBCUDACXX_COMPILER_CLANG_CUDA
 #endif
 
-#ifdef __CUDACC__
+#if defined(__CUDACC__) || defined(_NVHPC_CUDA)
 #  define _LIBCUDACXX_CUDACC
 #  define _LIBCUDACXX_CUDACC_VER_MAJOR __CUDACC_VER_MAJOR__
 #  define _LIBCUDACXX_CUDACC_VER_MINOR __CUDACC_VER_MINOR__