Remove references to an undefined include directories variable

The tests and benchmarks still referenced the include directories of
the private dependencies after the variable had been removed. These
directories are already provided by linking the dependency targets.

Drop the references.

Change-Id: Ib569b0a53b00b6e33b70f21e216ff357c317a574

internal/ceres/CMakeLists.txt

diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 8ab92e2..77f790c 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -374,11 +374,9 @@
 
     # Pull in local headers from the generated test directories when ceres_test()
     # is invoked there, as well as the private headers in this directory which
-    # may be referenced without the 'ceres' path prefix and all private
-    # dependencies that may be directly referenced.
+    # may be referenced without the 'ceres' path prefix.
     target_include_directories(${NAME}_test
-      PRIVATE ${Ceres_SOURCE_DIR}/internal/ceres
-      ${CERES_LIBRARY_PRIVATE_DEPENDENCIES_INCLUDE_DIRS})
+      PRIVATE ${Ceres_SOURCE_DIR}/internal/ceres)
 
     # Some tests include direct references/includes of private dependency
     # headers which are not propagated via the ceres targets, so link them
@@ -509,8 +507,7 @@
 
 macro(add_dependencies_to_benchmark BENCHMARK_TARGET)
   target_include_directories(${BENCHMARK_TARGET}
-    PRIVATE ${Ceres_SOURCE_DIR}/internal
-            ${CERES_LIBRARY_PRIVATE_DEPENDENCIES_INCLUDE_DIRS})
+    PRIVATE ${Ceres_SOURCE_DIR}/internal)
   # Benchmarks include direct references/includes of private
   # dependency headers which are not propagated via the ceres targets,
   # so link them explicitly.