Incompatibility with minimize_crash=1

[zeux]

We've been using libprotobuf-mutator happily to fuzz an implementation of a programming language. One big obstacle however has been that crash minimization doesn't seem to work properly with this.

Specifically, when running the minimization with minimize_crash=1 it looks as if the fuzzer stops using the mutator and does byte-based mutation instead, which in practice basically never shrinks the test case in an interesting way.

Is this expected? Is this a limitation of this library or of libFuzzer itself?