Compiler/Emitter behavior consistency and improvement

[allenjzhang]

Compiler improvements:

• Display emitters being invoked. This is helpful when there are multiple emitters, users will be able to see the progress.
• When multiple emitters run, if one emitter fails, currently compiler skip the rest. We should decide whether we want to change the behavior to run all. If not, minimally should display message telling user we have skipped the rest of xxx emitters.
• When crash happens, write out detailed log including callstack in a temp file instead of showing on console

Consistent behavior among emitters

• Currently C# directly write out to console on files generated while other emitters writes nothing. They should be consistent. We should decide what's the rule and ways to allow emitter/user to see message at different level.
• Proposed rules:
  • When dealing with KNOWN bad states, each emitter should use diagnostic report at the consistent level.
  • For UNKNOWN bad states, they are allow to throw which generates callstacks & display File a bug message.
• Each emitter output same given an empty spec
• Champion scenario specs & common known bad state specs should be checked into Spector http-spec for regression tracking

More to add?