Build and shim improvements (AssemblyScript#1446)

* Use parallel mode for Terser
* Improve hrtime shim code

Author: MaxGraey

cli/shim/process.js

@@ -45,12 +45,12 @@ var performanceNow =
   function(){ return (new Date()).getTime(); };
 
 function hrtime(previousTimestamp) {
-  var clocktime = performanceNow.call(performance) * 1e-3;
-  var seconds = Math.floor(clocktime);
-  var nanoseconds = Math.floor((clocktime % 1) * 1e9);
+  var clocktime = performanceNow.call(performance);
+  var seconds = Math.floor(clocktime * 1e-3);
+  var nanoseconds = Math.floor(clocktime * 1e6 - seconds * 1e9);
   if (previousTimestamp) {
-    seconds = seconds - previousTimestamp[0];
-    nanoseconds = nanoseconds - previousTimestamp[1];
+    seconds -= previousTimestamp[0];
+    nanoseconds -= previousTimestamp[1];
     if (nanoseconds < 0) {
       seconds--;
       nanoseconds += 1e9;

webpack.config.js

@@ -53,6 +53,7 @@ const lib = {
             preamble: preamble("The AssemblyScript Compiler.")
           }
         },
+        parallel: true,
         sourceMap: true
       })
     ],
@@ -120,6 +121,7 @@ const bin = {
             preamble: preamble("The AssemblyScript Compiler Frontend.")
           }
         },
+        parallel: true,
         sourceMap: true
       })
     ],