dpkg-buildpackage: Make dependency checks fatal for -S

When we are doing a source-only build the dependency checks are required
to be able to safely call the clean target. If the user also specifies
-nc then the dependency checks will be omitted.

debian/changelog

@@ -125,6 +125,7 @@ dpkg (1.18.0) UNRELEASED; urgency=low
     “3.0 (quilt)” too.
   * Add dpkg --ctrl-tarfile forwarding command for dpkg-deb.
   * Disable dependency checks on dpkg-buildpackage -S -nc.
+  * Make dependency checks fatal for dpkg-buildpackage -S.
 
   [ Raphaël Hertzog ]
   * Drop myself from Uploaders.

scripts/dpkg-buildpackage.pl

@@ -503,13 +503,7 @@ if ($checkbuilddep) {
     } elsif (WEXITSTATUS($?)) {
 	warning(g_('build dependencies/conflicts unsatisfied; aborting'));
 	warning(g_('(Use -d flag to override.)'));
-
-	if (build_sourceonly) {
-	    warning(g_('this is currently a non-fatal warning with -S, but ' .
-	               'will probably become fatal in the future'));
-	} else {
-	    exit 3;
-	}
+	exit 3;
     }
 }