old_contents: from spack import *
  
  class Libtool(Package):
      """libtool -- library building part of autotools"""
      homepage = "https://www.gnu.org/software/libtool/"
      url      = "http://ftpmirror.gnu.org/libtool/libtool-2.4.2.tar.gz"
  
      version('2.4.6' , 'addf44b646ddb4e3919805aa88fa7c5e')
      version('2.4.2' , 'd2f3b7d4627e69e13514a40e72a24d50')
  
      def install(self, spec, prefix):
          configure("--prefix=%s" % prefix)
  
          make()
          make("install")
  
new_contents: from spack import *
  
  class Libtool(Package):
      """libtool -- library building part of autotools"""
      homepage = "https://www.gnu.org/software/libtool/"
      url      = "http://ftpmirror.gnu.org/libtool/libtool-2.4.2.tar.gz"
  
      version('2.4.6' , 'addf44b646ddb4e3919805aa88fa7c5e')
      version('2.4.2' , 'd2f3b7d4627e69e13514a40e72a24d50')
  
      depends_on('m4')
  
      def install(self, spec, prefix):
          configure("--prefix=%s" % prefix)
  
          make()
          make("install")
  
subject: add a missing dependency