[fuzzing] Make fuzzing resource proper targets

This CL changes the corpora, dictionary, and options files to be
produced by GN targets rather than just "write_file" directives.
Previously, the build worked only because these files were emitted when
the component manifest target was invoked.  For zircon fuzzers, no .cmx
file is needed, so the dependency needs to be explicit.

SEC-103 #comment This should make the zircon fuzzers usable in garnet

Tests: Manually built and booted
Change-Id: I8e422036b80c55fb542225a0b99291d755d6d414
3 files changed