handle $(eval foo := $(var)) case

before:
% ./run_integration_test.rb android
Running make for android... 5.84 secs
Running kati for android... 18.94 secs
android: OK

PASS!

after:
% ./run_integration_test.rb android
Running make for android... 5.83 secs
Running kati for android... 16.83 secs
android: OK

PASS!
2 files changed