Changed CMake setup to use targets instead of variables (#269)

* Moved json to a target

* Moved other dependencies to targets

* Removed cmake Python version requirement

CMakeLists.txt

@@ -17,7 +17,8 @@ set(CMAKE_CXX_STANDARD 11)
 # Third Party Dependencies
 find_package(GSL    REQUIRED)
 find_package(Eigen3 3.3 REQUIRED NO_MODULE)
-find_package(PythonLibs REQUIRED COMPONENTS Development Interpreter Compiler)
+find_package(Python REQUIRED COMPONENTS Development)
+find_package(nlohmann_json REQUIRED)
 
 # Library setup
 add_library(ale SHARED
@@ -25,21 +26,19 @@ add_library(ale SHARED
 set_target_properties(ale PROPERTIES
     VERSION ${PROJECT_VERSION}
     SOVERSION 1)
-set(ALE_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/include/"
-                     "${CMAKE_CURRENT_SOURCE_DIR}/include/json")
+set(ALE_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/include/")
 
 target_include_directories(ale
-                           PRIVATE
-                           ${GSL_INCLUDE_DIRS}
-                           ${EIGEN3_INCLUDE_DIR}
-                           ${PYTHON_INCLUDE_DIR}
                            PUBLIC
                            ${ALE_INCLUDE_DIRS})
 
  target_link_libraries(ale
                        PRIVATE
-                       ${GSL_LIBRARIES}
-                       ${PYTHON_LIBRARY})
+                       GSL::gsl
+                       GSL::gslcblas
+                       Eigen3::Eigen
+                       Python::Python
+                       nlohmann_json::nlohmann_json)
 
 # Optional build tests
 option (BUILD_TESTS "Build tests" ON)
@@ -52,7 +51,8 @@ if(BUILD_TESTS)
 
   target_link_libraries(ale
                         PRIVATE
-                        ${GSL_LIBRARIES}
+                        GSL::gsl
+                        GSL::gslcblas
                         ${PYTHON_LIBRARY}
                         PUBLIC
                         gtest ${CMAKE_THREAD_LIBS_INIT})