Add a --dev flag that disables our JIT and forces Hotspot tier 1.

Specifying the --dev flag adds the following JVM flags to startup:

-XX:+TieredCompilation
-XX:TieredStopAtLevel=1
-Djruby.compile.mode=OFF

Author: headius

argnames.h

@@ -24,6 +24,7 @@
 /* Below are standard JRuby args handled by the launcher. */
 #define ARG_NAME_SERVER "--server"
 #define ARG_NAME_CLIENT "--client"
+#define ARG_NAME_DEV "--dev"
 #define ARG_NAME_SAMPLE "--sample"
 #define ARG_NAME_MANAGE "--manage"
 #define ARG_NAME_HEADLESS "--headless"

argparser.cpp

@@ -316,6 +316,11 @@ bool ArgParser::parseArgs(int argc, char *argv[]) {
         } else if (it->compare(ARG_NAME_SERVER) == 0
                 || it->compare(ARG_NAME_CLIENT) == 0) {
             javaOptions.push_back(it->substr(1)); // to JVMLauncher, -server instead of --server
+        } else if (it->compare(ARG_NAME_DEV) == 0) {
+            javaOptions.push_back("-XX:+TieredCompilation");
+            javaOptions.push_back("-XX:TieredStopAtLevel=1");
+            javaOptions.push_back("-Djruby.compile.mode=OFF");
+            progArgs.push_back(*it); // allow JRuby to process it too
         } else if (it->compare(ARG_NAME_SAMPLE) == 0) {
             javaOptions.push_back("-Xprof");
         } else if (it->compare(ARG_NAME_MANAGE) == 0) {