Annotate anonymous mmap #515

Job	Run time
cargo clippy	45s
make (yjit-bindgen, To fix: use patch in logs, --with-gcc=clang-12 --enable-yjit=dev)	4m 48s
cargo test	38s
make (check, RUSTC='rustc +1.58.0', 1.58.0)	8m 27s
make (check, --enable-yjit=dev)	13m 9s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc, -T --yj...	16m 54s
make (test-bundled-gems, --enable-yjit=dev)	20m 5s
make (yjit-bench, --enable-yjit=dev, --yjit-stats, true)	6m 1s
YJIT Ubuntu result	1s
	1h 10m 48s

Provide feedback