jit_support.rb: deal with -std=c99 flag

CC is changed from "icc" to "icc -std=c99" by r66605.

https://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-trunk/log/20181228T130003Z.fail.html.gz

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66615 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/lib/jit_support.rb

@@ -4,7 +4,7 @@ module JITSupport
   JIT_TIMEOUT = 600 # 10min for each...
   JIT_SUCCESS_PREFIX = 'JIT success \(\d+\.\dms\)'
   UNSUPPORTED_COMPILERS = [
-    %r[\Aicc\z],
+    %r[\Aicc\b],
     %r[\A/opt/developerstudio\d+\.\d+/bin/cc\z],
   ]