* gnu/packages/ntp.scm (ntp): Update to 4.2.8. Add openssl to inputs. Add pkg-config to native-inputs. Change source URI to archive.ntp.org.
* gnu/packages/ntp.scm (ntp)[inputs]: New field.
* gnu/packages/ntp.scm: New file. * gnu-system.am (gnu/packages/ntp.scm): Add it.