enabling warnings as error per target

[Matt Landis]

Hi,

I'd like to make it possible to incrementally enable scalac warnings as errors on a codebase that has probably 100k+ warnings.  It seems reasonable, as a novice wrt pants internals, to add something like a default_scalac_warnings_as_errors compile.zinc option that can be set in pants.ini, and then add a scalac_warnings_as_errors param to the scala_library target so individual targets can turn this on or off.

I might later do the same for scalastyle, checkstyle, and javac warnings as errors.

Is this (or something like it) something you'd want in OSS pants, or should I implement it internally?

Thanks,

Matt