Add prism to OSS-Fuzz

[tranquac]

New Project: prism (C library)

Adds continuous fuzzing for https://github.com/ruby/prism by fuzzing libprism directly as a standalone C library, not through the Ruby extension.

This revision addresses feedback from @Earlopain in ruby/prism#4073 who correctly pointed out that prism is also a C library and should be fuzzed at that level.

Fuzz targets

Target	Entry point	Coverage
fuzz_parse	pm_serialize_parse()	Full AST parse path — uses upstream fuzz/parse.c
fuzz_lex	pm_serialize_lex()	Lexer-only path — fuzz_lex.c

Build

ruby templates/template.rb   # generate templated C sources
make static CC=$CC CFLAGS=$CFLAGS   # build libprism.a with sanitizer flags
$CC/$CXX + $LIB_FUZZING_ENGINE      # link harnesses against library

Sanitizers

address, memory (msan — not possible with Ruby extension), undefined

Corpus & dictionary

• Seed corpus: ~986 Ruby fixture files from test/prism/fixtures/ (all subdirs)
• Dictionary: fuzz/dict from the project (Ruby keywords, operators, magic tokens)

Build verification

• build_image ✓
• build_fuzzers --sanitizer address ✓
• check_build --sanitizer address ✓
• Smoke tests: both targets run clean, no crashes

Project maintainer: @kddnewton (Kevin Newton, kddnewton@gmail.com)

[github-actions]

tranquac is integrating a new project:
- Main repo: https://github.com/ruby/prism
- Criticality score: 0.58048