cmake: use GNUInstallDirs to setup the install paths

GNUInstallDirs provides variables for the bin/, lib64/, etc. paths.

Use the CMAKE_INSTALL_LIBDIR that is provided by GNUInstallDirs rather
than calculating our own value.

CMakeLists.txt

@@ -44,14 +44,7 @@ SET( ${PROJECT_NAME}_MAJOR_VERSION 0 )
 SET( ${PROJECT_NAME}_MINOR_VERSION 1 )
 SET( ${PROJECT_NAME}_PATCH_LEVEL 0 )
 
-# output executable and library path
-# The library directory is configured by setting CMAKE_INSTALL_LIBDIR.
-# Otherwise, the defaults set here are used.
-IF(EXISTS "/usr/lib64" AND NOT IS_SYMLINK "/usr/lib64")
-    SET(CMAKE_INSTALL_LIBDIR "lib64" CACHE STRING "Library Directory Basename")
-ELSE()
-    SET(CMAKE_INSTALL_LIBDIR "lib" CACHE STRING "Library Directory Basename")
-ENDIF()
+include(GNUInstallDirs)
 
 ## Setup platform specific helper defines build variants
 IF(WIN32)
@@ -113,5 +106,3 @@ ADD_SUBDIRECTORY (src/tools)
 ADD_SUBDIRECTORY (src/py)
 ADD_SUBDIRECTORY (src/tests)
 ADD_SUBDIRECTORY (src/doc)
-
-