Update Cuda memcheck test

* Previously the Cuda memcheck tests relied on the Cuda binaries being
  on the environment PATH. This has been changed instead to use the
  path discovered by CMake when searching for Cuda. This has the added
  benefit that the memcheck tool will be sure to be from the same Cuda
  version install as the version being compiled against.

Change-Id: I650d1bb7e14064ca98a01e3c13eb1bcb772b51cc
diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 5b8c1ea..5e7c349 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -134,10 +134,10 @@
   if (BUILD_TESTING)
     add_test(
         NAME cuda_memcheck_dense_qr_test
-        COMMAND cuda-memcheck --leak-check full
+        COMMAND ${CUDA_TOOLKIT_ROOT_DIR}/bin/cuda-memcheck --leak-check full
             $<TARGET_FILE:cuda_dense_qr_test>)
     add_test(
-        NAME cuda_memcheck_dense_cholesky_test
+        NAME ${CUDA_TOOLKIT_ROOT_DIR}/bin/cuda_memcheck_dense_cholesky_test
         COMMAND cuda-memcheck --leak-check full
             $<TARGET_FILE:cuda_dense_cholesky_test>)
   endif (BUILD_TESTING)