Fix Python include issue introduced in 17d4cb2

The CMake FOUND variable is different for CMake < 3.12

Allow to work on Ubuntu 18.04 with ROS Melodic and CMake 3.10

Should fix #161

Author: romainreignier

ct_core/CMakeLists.txt

@@ -99,13 +99,15 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/include/ct/core/templateDir.h.in ${CM
 
 ## define the directories to be included in all ct_core targets
 list(APPEND ct_core_target_include_dirs ${EIGEN3_INCLUDE_DIR})
-if(${Python_FOUND})
-	if(${CMAKE_VERSION} VERSION_LESS "3.12.0")
-	    list(APPEND ct_core_target_include_dirs ${PYTHON_INCLUDE_DIRS})
-	else()
-	    list(APPEND ct_core_target_include_dirs ${Python_INCLUDE_DIRS})
-	    list(APPEND ct_core_target_include_dirs ${Python_NumPy_INCLUDE_DIRS})
-	endif()
+if(${CMAKE_VERSION} VERSION_LESS "3.12.0")
+    if(PYTHONLIBS_FOUND)
+        list(APPEND ct_core_target_include_dirs ${PYTHON_INCLUDE_DIRS})
+    endif()
+else()
+    if(Python_FOUND AND ${Python_VERSION_MAJOR} EQUAL 3)
+        list(APPEND ct_core_target_include_dirs ${Python_INCLUDE_DIRS})
+        list(APPEND ct_core_target_include_dirs ${Python_NumPy_INCLUDE_DIRS})
+    endif()
 endif()
 list(APPEND ct_core_target_include_dirs ${QWT_INCLUDE_DIR})
 list(APPEND ct_core_target_include_dirs $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)