[gcc] add binutils to $PATH when using SlapOS GCC

When system GCC is too old, SlapOS GCC may produce binaries
that 'strip' does not process correctly.

component/defaults.cfg

@@ -72,6 +72,7 @@ update =
     env = os.environ
     env['PATH'] = os.pathsep.join((
       os.path.join(options['prefix'], 'bin'),
+      os.path.join(self.buildout['binutils']['location'], 'bin'),
       env['PATH']
     ))
   else: