mkmf.rb: -I flags to $INCFLAGS
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47458 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: -I flags to $INCFLAGS
$INCFLAGS, which is used by CPP.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47458 b2dd03c8-39d4-4d8f-98ff-823fe69b080e