Returns a string with the include folders

def include_flags(self, arch):
        '''Returns a string with the include folders'''
        openssl_includes = join(self.get_build_dir(arch.arch), 'include')
        return (' -I' + openssl_includes +
                ' -I' + join(openssl_includes, 'internal') +
                ' -I' + join(openssl_includes, 'openssl'))