configure.in: BOOTSTRAPRUBY version

* configure.in (BOOTSTRAPRUBY): avoid too old versions.  current
  fileutils.rb does not work with 1.8 or older, because of the
  return values of Module#singleton_methods and so on.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51789 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -3435,7 +3435,9 @@ else
   RUNRUBY='$(RUNRUBY_COMMAND) --'
   XRUBY='$(RUNRUBY)'
   BOOTSTRAPRUBY='$(MINIRUBY)'
-  test x"${HAVE_BASERUBY}" = xyes && BOOTSTRAPRUBY='$(BASERUBY)'
+  test x"${HAVE_BASERUBY}" = xyes &&
+  ${BASERUBY} -e 'exit module A;def foo;end;instance_methods;end.include?(:foo)' &&
+  BOOTSTRAPRUBY='$(BASERUBY)'
   TEST_RUNNABLE=yes
   CROSS_COMPILING=no
 fi