FindCUDA: Fix support for backslashes in CUDA_NVCC_INCLUDE_DIRS

Backslashes in `CUDA_NVCC_INCLUDE_DIRS` cause syntax errors because it
is written to a generated `.cmake` script as a string literal.  Use a
bracket argument to hold the expanded value as we already do for
`CUDA_NVCC_COMPILE_DEFINITIONS`.  Then explicitly convert backslashes to
forward slashes.

Modules/FindCUDA/run_nvcc.cmake

@@ -75,7 +75,8 @@ set(CUDA_NVCC_EXECUTABLE "@CUDA_NVCC_EXECUTABLE@") # path
 set(CUDA_NVCC_FLAGS @CUDA_NVCC_FLAGS@ ;; @CUDA_WRAP_OPTION_NVCC_FLAGS@) # list
 @CUDA_NVCC_FLAGS_CONFIG@
 set(nvcc_flags @nvcc_flags@) # list
-set(CUDA_NVCC_INCLUDE_DIRS "@CUDA_NVCC_INCLUDE_DIRS@") # list (needs to be in quotes to handle spaces properly).
+set(CUDA_NVCC_INCLUDE_DIRS [==[@CUDA_NVCC_INCLUDE_DIRS@]==]) # list (needs to be in lua quotes to address backslashes)
+string(REPLACE "\\" "/" CUDA_NVCC_INCLUDE_DIRS "${CUDA_NVCC_INCLUDE_DIRS}")
 set(CUDA_NVCC_COMPILE_DEFINITIONS [==[@CUDA_NVCC_COMPILE_DEFINITIONS@]==]) # list (needs to be in lua quotes see #16510 ).
 set(format_flag "@format_flag@") # string
 set(cuda_language_flag @cuda_language_flag@) # list