dpkg.cfg: Reintroduce 'no-debsig' option

This avoids failing to install any package when debsig-verify is installed,
as distributions do not use embedded signatures in packages. Closes: #311843

debian/changelog

@@ -15,6 +15,8 @@ dpkg (1.14.17) UNRELEASED; urgency=low
     Christian Perrier with their permission.
   * Use functions from libcompat when those are not provided by the system.
   * Change dpkg-gencontrol to not output the Homapage field on udeb.
+  * Reintroduce 'no-debsig' back in dpkg.cfg to avoid failing to install any
+    package when debsig-verify is installed. Closes: #311843
 
   [ Raphael Hertzog ]
   * Add a warning displayed by dpkg-genchanges if the current version is

debian/dpkg.cfg

@@ -5,5 +5,9 @@
 # the option, separated by whitespace and/or an `=' sign.
 #
 
+# Do not enable debsig-verify by default; since the distribution is not using
+# embedded signatures, debsig-verify would reject all packages.
+no-debsig
+
 # Log status changes and actions to a file.
 log /var/log/dpkg.log