This prevents needing a special case in the fuzz tests to detect
valgrind usage and a new exec. Instead, we simply detect the environment
in a shell script and start the test with valgrind in the first place.
* fuzz/test-runner.sh: New script for running the fuzz tests
* fuzz/main.c (main): Remove code for re-running under valgrind
* fuzz/Makefile.am: Set the LOG_COMPILER to test-runner.sh and remember
to add it to the list of extra files for packaging
