Use LIB_SUFFIX to install to lib64 instead of lib (thanks, Cristian!).

CMakeLists.txt

@@ -554,8 +554,8 @@ ENDIF(PHYSFS_BUILD_RUBY)
 
 INSTALL(TARGETS ${PHYSFS_INSTALL_TARGETS}
         RUNTIME DESTINATION bin
-        LIBRARY DESTINATION lib
-        ARCHIVE DESTINATION lib)
+        LIBRARY DESTINATION lib${LIB_SUFFIX}
+        ARCHIVE DESTINATION lib${LIB_SUFFIX})
 INSTALL(FILES src/physfs.h DESTINATION include)
 
 FIND_PACKAGE(Doxygen)