Ensure that build fails are logged at the right times

Builds should fail with logging during the failure, not at the end. This
reverts back to the behaviour prior to yui#115.

Build fails still call the appropriate callback function.

lib/builder.js

@@ -83,8 +83,12 @@ exports.start = function (json, options, buildCallback) {
         buildStat,
         end = function (err) {
             var end = new Date();
-            log.info('done racing, the gears are toast');
-            log.info('finished in ' + timer.calc(start, end) + ', pretty fast huh?');
+            if (err) {
+                log.err('Build failed: Errors encountered during build');
+            } else {
+                log.info('done racing, the gears are toast');
+                log.info('finished in ' + timer.calc(start, end));
+            }
             if (buildCallback) {
                 buildCallback(err);
             }

lib/index.js

@@ -46,10 +46,16 @@ var runQueue = function() {
     }
 };
 
+function standardExitCallback(err) {
+    if (err) {
+        process.exit(1);
+    }
+}
+
 function logAndExit(err) {
     if (err) {
         log.err(err);
-        process.exit(1);
+        standardExitCallback(err);
     }
 }
 
@@ -70,7 +76,7 @@ exports.init = function (opts, initCallback) {
     log.reset(options);
 
     if (!initCallback) {
-        initCallback = logAndExit;
+        initCallback = standardExitCallback;
     }
 
     if (options.cwd) {