dpkg-deb: Do not warn on strange timestamps

The external extractor is only used on dpkg-deb -x (and friends), which
is only used by dpkg when extracting the control member. The internal
dpkg tar extractor never warns on timestamps, and there's no point for
dpkg to induce those warnings on the control extraction either.

Closes: #640298

debian/changelog

@@ -209,6 +209,8 @@ dpkg (1.16.1) UNRELEASED; urgency=low
     Based on a patch by Salvatore Bonaccorso <carnil@debian.org>.
   * Fix double “error:” string in dpkg missing PATH error output.
     Closes: #639997
+  * Do not warn on strange timestamps when unpacking with dpkg-deb.
+    Closes: #639997
 
   [ Updated dpkg translations ]
   * German (Sven Joachim). Closes: #620312

dpkg-deb/extract.c

@@ -313,7 +313,7 @@ extracthalf(const char *debar, const char *dir, const char *taroption,
         }
       }
 
-      execlp(TAR, "tar", buffer, "-", NULL);
+      execlp(TAR, "tar", buffer, "-", "--warning=no-timestamp", NULL);
       ohshite(_("unable to execute %s (%s)"), "tar", TAR);
     }
     close(p2[0]);