message: document -Zmiri-seed
diff: @@ -231,15 +231,23 @@ MIRI_SYSROOT=$(rustc +custom --print sysroot) cargo +custom run --manifest-path
  Several `-Z` flags are relevant for Miri:
  -* `-Zmir-opt-level` controls how many MIR optimizations are performed. miri
  +* `-Zmiri-seed=<hex>` is a custom `-Z` flag added by Miri. It enables the
  + interpreted program to seed an RNG with system entropy. Miri will keep an RNG
  + on its own that is seeded with the given seed, and use that to generate the
  + "system entropy" that seeds the RNG(s) in the interpreted program.
  + **NOTE**: This entropy is not good enough for cryptographic use! Do not
  + generate secret keys in Miri or perform other kinds of cryptographic
  + operations that rely on proper random numbers.
  +* `-Zmiri-disable-validation` disables enforcing the validity invariant, which
  + is enforced by default. This is mostly useful for debugging; it means Miri
  + will miss bugs in your program. However, this can also help to make Miri run
  + faster.
  +* `-Zmir-opt-level` controls how many MIR optimizations are performed. Miri
  overrides the default to be `0`; be advised that using any higher level can
  - make miri miss bugs in your program because they got optimized away.
  + make Miri miss bugs in your program because they got optimized away.
  * `-Zalways-encode-mir` makes rustc dump MIR even for completely monomorphic
  - functions. This is needed so that miri can execute such functions, so miri
  + functions. This is needed so that Miri can execute such functions, so Miri
  sets this flag per default.
  -* `-Zmiri-disable-validation` is a custom `-Z` flag added by miri. It disables
  - enforcing the validity invariant, which is enforced by default. This is
  - mostly useful for debugging; it means miri will miss bugs in your program.
  Moreover, Miri recognizes some environment variables:
  