This is to help with frequent build breakages cased by proto changes.
Fuzzer corpus can be periodically auto-regenerated.
Crashing samples from the fuzzer are better 'preserved' in the form of fail_xx.carbon tests.
The logic is using bazel Runfiles API per Jon's suggestion.
One of the scenarios used by the fuzzing framework is to place the binary and its runfiles into a folder, resulting in a directory layout like this:
[temp dir]
fuzzer
fuzzer.runfiles/
Tested:
bazel test -c opt explorer/fuzzing:explorer_fuzzer
bazel build -c opt explorer/fuzzing:explorer_fuzzer + run the binary from various locations