Use INSTALL_LIB_DIR instead of 'CMAKE_INSTALL_PREFIX/lib' in CMakeLis…

…ts.txt (drogonframework#318)

CMakeLists.txt

@@ -8,17 +8,6 @@ option(BUILD_ORM "Build orm" ON)
 option(LIBPQ_BATCH_MODE "Use batch mode for libpq" ON)
 option(BUILD_DROGON_SHARED "Build drogon as a shared lib" OFF)
 
-if(BUILD_DROGON_SHARED)
-  set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
-  list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/lib" isSystemDir)
-  if("${isSystemDir}" STREQUAL "-1")
-     set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
-  endif("${isSystemDir}" STREQUAL "-1")
-  add_library(${PROJECT_NAME} SHARED)
-else()
-  add_library(${PROJECT_NAME} STATIC)
-endif()
-
 set(DROGON_MAJOR_VERSION 1)
 set(DROGON_MINOR_VERSION 0)
 set(DROGON_PATCH_VERSION 0)
@@ -52,6 +41,17 @@ foreach(p
   endif()
 endforeach()
 
+if(BUILD_DROGON_SHARED)
+  set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
+  list(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${INSTALL_LIB_DIR}" isSystemDir)
+  if("${isSystemDir}" STREQUAL "-1")
+     set(CMAKE_INSTALL_RPATH "${INSTALL_LIB_DIR}")
+  endif("${isSystemDir}" STREQUAL "-1")
+  add_library(${PROJECT_NAME} SHARED)
+else()
+  add_library(${PROJECT_NAME} STATIC)
+endif()
+
 include(CheckIncludeFileCXX)
 
 check_include_file_cxx(any HAS_ANY)