Make mx espresso run either native or jvm based on availability

* `mx espresso-launcher` always run in jvm mode.

Author: gilles-duboscq

espresso/mx.espresso/mx_espresso.py

@@ -969,7 +969,8 @@ def gen_gc_option_check(args):
 
 # Register new commands which can be used from the commandline with mx
 mx.update_commands(_suite, {
-    'espresso': [_run_espresso_launcher, '[args]'],
+    'espresso': [_run_espresso, '[args]'],
+    'espresso-launcher': [_run_espresso_launcher, '[args]'],
     'espresso-embedded': [_run_espresso_embedded, '[args]'],
     'java-truffle': [_run_java_truffle, '[args]'],
     'espresso-meta': [_run_espresso_meta, '[args]'],