Dafny fails, but returns exit status of zero

[0xabu]

Dafny generally gets the exit status correct for verification, but some invocations that emit an error message incorrectly return an exit status of zero. This is a minor bug, but still isn't good for a parent build system.

For example, in both of these cases Dafny has clearly failed (at a different stage) and printed an error message, but it returned a zero exit status:

% Dafny.exe /noNLarith /timeLimit:60 /trace /compile:0 main.i.dfy
[TRACE] Using prover: C:\Users\baumann\src\spartan\tools\Mindy\Binaries\z3.exe
Dafny program verifier version 1.9.7.30401, Copyright (c) 2003-2016, Microsoft.
Parsing main.i.dfy
smc_handler.gen.dfy(1499,7): Error: more than one declaration of function/procedure name: CheckWellformed$$_.Main
smc_handler.gen.dfy(1499,7): Error: more than one declaration of function/procedure name: IntraModuleCall$$_.Main
2 name resolution errors detected in C:\cygwin64\tmp\main.i.bpl

*** Encountered internal translation error - re-running Boogie to get better debug information

C:\cygwin64\tmp\main.i.bpl(6013,10): Error: more than one declaration of function/procedure name: CheckWellformed$$_.Main
C:\cygwin64\tmp\main.i.bpl(6018,10): Error: more than one declaration of function/procedure name: IntraModuleCall$$_.Main
2 name resolution errors detected in C:\cygwin64\tmp\main.i.bpl

% Dafny.exe /trace /noVerify /compile:2 /out:main.exe main.i.dfy
[TRACE] Using prover: C:\Users\baumann\src\spartan\tools\Mindy\Dafny\z3.exe
Dafny program verifier version 1.9.7.30401, Copyright (c) 2003-2016, Microsoft.
Parsing main.i.dfy
Coalescing blocks...
Inlining...

Running abstract interpretation...
  [0.0624617 s]

Dafny program verifier finished with 0 verified, 0 errors
Compilation error: an assume statement cannot be compiled (line 188)
Compilation error: an assume statement cannot be compiled (line 235)