Merge topic 'cross_ref_CUDAHOSTCXX_in_CMAKE_CUDA_HOST_COMPILER'

d3ebef4f70 CMAKE_CUDA_HOST_COMPILER: Document it takes priority over CUDAHOSTCXX

Acked-by: Kitware Robot <[email protected]>
Merge-request: !3490

Help/variable/CMAKE_CUDA_HOST_COMPILER.rst

@@ -4,4 +4,5 @@ CMAKE_CUDA_HOST_COMPILER
 Executable to use when compiling host code when compiling ``CUDA`` language
 files. Maps to the ``nvcc -ccbin`` option.  Will only be used by CMake on the first
 configuration to determine a valid host compiler for ``CUDA``. After a valid
-host compiler has been found, this value is read-only.
+host compiler has been found, this value is read-only.  This variable takes
+priority over the :envvar:`CUDAHOSTCXX` environment variable.