Fixes for RPM packaging issues (on CentOS 8):

* add "common" package provides for `libcedar.so()(64bit)` to allow `softether-vpnserver` package to install properly

* exclude `/lib/systemd/system` paths from RPM package file listing to prevent file conflicts when installing RPM (these paths already are "owned" by the systemd RPM)

CMakeLists.txt

@@ -87,6 +87,7 @@ if(UNIX)
   set(CPACK_RPM_FILE_NAME "RPM-DEFAULT")
   set(CPACK_RPM_PACKAGE_GROUP "Applications/Internet")
   set(CPACK_RPM_PACKAGE_LICENSE "ASL 2.0")
+  set(CPACK_RPM_COMMON_PACKAGE_PROVIDES "libcedar.so()(64bit)")
 
   # Exclude system directories
   if(CPACK_GENERATOR STREQUAL "RPM")
@@ -96,6 +97,9 @@ if(UNIX)
         OUTPUT_VARIABLE CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION
         ERROR_QUIET)
   endif()
+  list(APPEND CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION "/lib")
+  list(APPEND CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION "/lib/systemd")
+  list(APPEND CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION "/lib/systemd/system")
 
   include(CPack)
 endif()