appveyor.yml: use -fs for test-spec

to debug silent death on vs120 builds
https://ci.appveyor.com/project/ruby/ruby/builds/19630104/job/tm8at8kfnvwxwe58
https://ci.appveyor.com/project/ruby/ruby/builds/19631779/job/qpjanaho1lc1e5a0

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65172 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

appveyor.yml

@@ -95,7 +95,7 @@ for:
     - nmake -l "TESTOPTS=-q -j%JOBS% --subprocess-timeout-scale=1.5 --exclude win32ole --exclude test_syntax --exclude test_open-uri" test-all RUBY_FORCE_TEST_JIT=1
     # separately execute tests that may crash worker without -j.
     - nmake -l "TESTOPTS=-q --subprocess-timeout-scale=1.5" test-all TESTS="../test/win32ole ../test/ruby/test_syntax.rb ../test/open-uri/test_open-uri.rb"
-    - nmake -l test-spec
+    - nmake -l test-spec MSPECOPT=-fs
 -
   matrix:
     only: