Rollup merge of #139850 - xizheyin:issue-138698, r=jieyouxu

Hide unstable print kinds within emit_unknown_print_request_help in stable channel

Fixes #138698

We need to get the channel from `matches`. However, since `matches`(Line 1169) is constructed after `rustc_optgroups` (Line1165, where `RustcOptGroup::value_hint` is generated, i.e. what `rustc --print print` prints), I've left it unchanged here for now.

https://github.com/rust-lang/rust/blob/2da29dbe8fe23df1c7c4ab1d8740ca3c32b15526/compiler/rustc_driver_impl/src/lib.rs#L1161-L1169

There is actually a way to manually parse the `--crate-name` parameter, but I'm afraid that's an unorthodox practice. So I conservatively just modified `emit_unknown_print_request_help` to print different parameters depending on whether they are nightly or not when passing the error parameter.

r? ```@jieyouxu```

0 files changed, 0 insertions, 0 deletions