Outputting label file should not trigger second pass

[Iambian]

When I was compiling my project using spasm-ng, I noticed that adding -L did not suppress or omit the second pass. This is undesirable and is inconsistent with the original versions of SPASM.

See #49

[jacobly0]

This was changed in 73c39ad because all of the variables in the label file were showing up as having a value of 0.

[geekbozu]

Since that commit there were various error handler changes made 7fc05b1 . Can you reproduce that bug with the new pull request? In our tests it functioned as expected.