Fix potential incomplete RPath for installed library

Solution taken from https://cmake.org/Wiki/CMake_RPATH_handling

CMakeLists.txt

@@ -51,6 +51,8 @@ endif()
 ################################################################################
 include(cmake/ConfigureCompiler.cmake)
 
+include(cmake/ConfigureRPath.cmake)
+
 ################################################################################
 ## Apply user-defined configuration
 ################################################################################

cmake/Config.cmake.in

@@ -1,4 +1,4 @@
-# - Config file for the FooBar package
+# - Config file for the Super4PCS package
 # It defines the following variables
 #  Super4PCS_INCLUDE_DIRS - include directories for Super4PCS
 #  Super4PCS_LIB_DIR    - libraries to link against

cmake/ConfigureRPath.cmake

@@ -0,0 +1,24 @@
+## This script comes from https://cmake.org/Wiki/CMake_RPATH_handling#Always_full_RPATH
+#
+# It is designed 'to make sure that the required libraries are always found
+# independent from LD_LIBRARY_PATH and the install location'
+
+# use, i.e. don't skip the full RPATH for the build tree
+SET(CMAKE_SKIP_BUILD_RPATH  FALSE)
+
+# when building, don't use the install RPATH already
+# (but later on when installing)
+SET(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
+
+SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
+
+# add the automatically determined parts of the RPATH
+# which point to directories outside the build tree to the install RPATH
+SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+
+
+# the RPATH to be used when installing, but only if it's not a system directory
+LIST(FIND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES "${CMAKE_INSTALL_PREFIX}/lib" isSystemDir)
+IF("${isSystemDir}" STREQUAL "-1")
+   SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
+ENDIF("${isSystemDir}" STREQUAL "-1")