gnu: libvirt: Make selected inputs native-inputs.

* gnu/packages/virtualization.scm (libvirt)[inputs]: Move perl, polkit, and
python from here...
[native-inputs]: ...to here.

gnu/packages/virtualization.scm

@@ -365,7 +365,6 @@ manage system or application containers.")
        ("gnutls" ,gnutls)
        ("dbus" ,dbus)
        ("qemu" ,qemu)
-       ("polkit" ,polkit)
        ("libpcap" ,libpcap)
        ("libnl" ,libnl)
        ("libuuid" ,util-linux)
@@ -373,8 +372,6 @@ manage system or application containers.")
        ("curl" ,curl)
        ("openssl" ,openssl)
        ("cyrus-sasl" ,cyrus-sasl)
-       ("perl" ,perl)
-       ("python" ,python-2)
        ("libyajl" ,libyajl)
        ("audit" ,audit)
        ("dmidecode" ,dmidecode)
@@ -384,7 +381,10 @@ manage system or application containers.")
        ("iptables" ,iptables)))
     (native-inputs
      `(("xsltproc" ,libxslt)
-       ("pkg-config" ,pkg-config)))
+       ("perl" ,perl)
+       ("pkg-config" ,pkg-config)
+       ("polkit" ,polkit)
+       ("python" ,python-2)))
     (home-page "https://libvirt.org")
     (synopsis "Simple API for virtualization")
     (description "Libvirt is a C toolkit to interact with the virtualization