Add option to optimize the JVM for short-runnning applications

Ideally, dotc should reuse a resident compiler and we should not fork sbt
for every task. Until this happens, this option is useful for
development. Fixes #222.

Usage:
$ sbt -DOshort=""
$ ./bin/dotc -Oshort foo.scala

1 files changed, 3 insertions, 0 deletions

diff --git a/bin/dotc b/bin/dotc
index cafd80f03..72ac3141a 100755
--- a/bin/dotc
+++ b/bin/dotc
@@ -185,6 +185,9 @@ case "$1" in
     -d|-debug) debug=true && shift ;;
     -q|-quiet) quiet=true && shift ;;
 
+    # Optimize for short-running applications, see https://github.com/lampepfl/dotty/issues/222
+    -Oshort) addJava "-XX:+TieredCompilation -XX:TieredStopAtLevel=1" && shift ;;
+
         -repl) main_class=$ReplMain && shift ;;
      -compile) main_class=$CompilerMain && shift ;;
          -run) main_class=$ReplMain && shift ;;