Set the build status properly for failing local builds

If a build has ‘preferLocalBuilds = true’ (or we're not using remote
building), and the build has a non-permanent failure, then the build
status should be "Aborted" rather than "Failed".  This is denoted by
an exit status of 100 from nix-store.

src/script/hydra-build

@@ -368,7 +368,7 @@ sub doBuild {
         $stopTime = time();
 
         if ($res != 0) {
-            if ($thisBuildFailed) { $buildStatus = 1; }
+            if ($thisBuildFailed && $res == 100) { $buildStatus = 1; }
             elsif ($someBuildFailed) { $buildStatus = 2; }
             else { $buildStatus = 3; }
         }