Add stub library that just feeds files to the fuzzing target.

This will allow the fuzzers to be run as part of "make check".

plugins/sudoers/regress/fuzz/fuzz_sudoers.c

@@ -97,12 +97,3 @@ LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
     return 0;
 }
-
-#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-int
-main(int argc, char *argv[])
-{
-    /* Nothing for now. */
-    return LLVMFuzzerTestOneInput(NULL, 0);
-}
-#endif