fix pkgconfig install path

Index: src/config/core/CMakeLists.txt
--- src/config/core/CMakeLists.txt.orig
+++ src/config/core/CMakeLists.txt
@@ -9,7 +9,7 @@ if(NOT WIN32)
   install(
     FILES
       "${CMAKE_CURRENT_BINARY_DIR}/liblucene++.pc"
-    DESTINATION "include/pkgconfig")
+    DESTINATION "lib/pkgconfig")
 endif()
 
 
