Disable SimpleCov on JRuby

Commit rspec/rspec-core@26dd955
was done in rspec-core but it should be done in rspec-dev since the file
is auto-generated.

Author: yujinakayama

travis/script/functions.sh

@@ -25,7 +25,7 @@ function run_specs_and_record_done {
 
   # rspec-core needs to run with a special script that loads simplecov first,
   # so that it can instrument rspec-core's code before rspec-core has been loaded.
-  if [ -f script/rspec_with_simplecov ]; then
+  if [ -f script/rspec_with_simplecov ] && is_mri; then
     rspec_bin=script/rspec_with_simplecov
   fi;