mkmf.rb: Do not modify caller strings
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53821 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: Do not modify caller strings
be modified, in append_{cpp,c,ld}flags respectively.
[Fix GH-1246]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53821 b2dd03c8-39d4-4d8f-98ff-823fe69b080e