Install calculate-meta if only it is not installed.

pym/cl_assemble.py

@@ -148,6 +148,8 @@ class cl_assemble(color_print):
               'progname':'perl-cleaner'},
              # install meta package
              {'command':'emerge --noreplace calculate-meta',
+              'checkcommand':'find /var/db/pkg/app-misc -name "calculate-meta*"',
+              'condition':'^$',
               'step':'meta'},
              # update packages with fix newuse
              #{'command':'emerge -D --newuse world',