Set cuda_root variable in cmakelists to make it show up in the gui when configuring.

Former-commit-id: 29ca44312f

CMakeLists.txt

@@ -29,6 +29,7 @@ option(LINK_LIBCXXABI "Sets whether libc++abi should be linked." OFF)
 option(USE_LIBCXX "Sets whether the standard library is libc++." OFF)
 set(GUROBI_ROOT "" CACHE STRING "The root directory of Gurobi (if available).")
 set(Z3_ROOT "" CACHE STRING "The root directory of Z3 (if available).")
+set(CUDA_ROOT "" CACHE STRING "The root directory of CUDA.")
 set(ADDITIONAL_INCLUDE_DIRS "" CACHE STRING "Additional directories added to the include directories.")
 set(ADDITIONAL_LINK_DIRS "" CACHE STRING "Additional directories added to the link directories.")
 set(CUSTOM_BOOST_ROOT "" CACHE STRING "A custom path to the Boost root directory.")