Fix cmake_package install being broken because of wrong include path.

The TARGET_INCLUDE_DIRECTORIES from inside the
IF(JSONCPP_WITH_CMAKE_PACKAGE) block was removed, since it only needs to
be set once.

In addition the CMAKE_VERSION check was simplified.

src/lib_json/CMakeLists.txt

@@ -49,18 +49,15 @@ ADD_LIBRARY( jsoncpp_lib ${JSONCPP_LIB_TYPE}
 SET_TARGET_PROPERTIES( jsoncpp_lib PROPERTIES OUTPUT_NAME jsoncpp )
 SET_TARGET_PROPERTIES( jsoncpp_lib PROPERTIES VERSION ${JSONCPP_VERSION} SOVERSION ${JSONCPP_VERSION_MAJOR} )
 
-IF(CMAKE_VERSION VERSION_EQUAL 2.8.11 OR CMAKE_VERSION VERSION_GREATER 2.8.11)
-    TARGET_INCLUDE_DIRECTORIES( jsoncpp_lib
-                                PUBLIC ${JSONCPP_INCLUDE_DIR}
+IF(NOT CMAKE_VERSION VERSION_LESS 2.8.11)
+    TARGET_INCLUDE_DIRECTORIES( jsoncpp_lib PUBLIC
+                                $<INSTALL_INTERFACE:${INCLUDE_INSTALL_DIR}>
+                                $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/${JSONCPP_INCLUDE_DIR}>
                                 )
-ENDIF(CMAKE_VERSION VERSION_EQUAL 2.8.11 OR CMAKE_VERSION VERSION_GREATER 2.8.11)
+ENDIF(NOT CMAKE_VERSION VERSION_LESS 2.8.11)
 
 # Install instructions for this target
 IF(JSONCPP_WITH_CMAKE_PACKAGE)
-    TARGET_INCLUDE_DIRECTORIES( jsoncpp_lib
-                                PUBLIC $<INSTALL_INTERFACE:${INCLUDE_INSTALL_DIR}>
-                                       $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/${JSON_INCLUDE_DIR}>
-                                )
     SET(INSTALL_EXPORT EXPORT jsoncpp)
 ELSE(JSONCPP_WITH_CMAKE_PACKAGE)
     SET(INSTALL_EXPORT)