compile error:" unused variable ‘root’ "

[Hatt Tom]

hi:

   I am compiling systemstap from source ,after configure well , I
type 'make' to compile .
   it print:
       tapset-method.cxx:431:15: error: unused variable ‘root’
[-Werror=unused-variable]
      tapset-method.cxx:432:26: error: unused variable ‘builder’
[-Werror=unused-variable]

how do I fix this issure?

thanks!