go fmt.
Cleanup comments.
Fix style and variable naming.
Clean up GOXC function.
Simplify appending to cmd.Env and cmd.Arg.
Style nit I missed previously.
Use filepath.Join.
Log proper script name.
Simplify if-else nesting.
Add option to output ZIP archives instead of dirs.
Remove commented-out code.
Set reported path to ZIP only when ZIP succeeds.
Set proper file attributes in ZIP archives.
Remove zip from TODO.
Add option 'codesign' to sign OS X binaries.
Merge pull request #1 from dchest/master

Cleanup; Add ZIP and codesign options