fuzz: libFuzzer build failure "unexpected `cfg` condition value: `max_level_*`"

[dergoegge]

Building the fuzz harnesses for fuzzing with libFuzzer is broken when using a recent rust nightly.

$ rustc --version
rustc 1.85.0-nightly (7db7489f9 2024-11-25)
$ RUSTFLAGS="--cfg=secp256k1_fuzz --cfg=hashes_fuzz" cargo +nightly fuzz build --features "libfuzzer_fuzz" msg_ping_target
...
error: unexpected `cfg` condition value: `max_level_debug`
   --> /workdir/rust-lightning/lightning-rapid-gossip-sync/src/processing.rs:447:6
    |
447 | /                     log_given_level!(
448 | |                         self.logger,
449 | |                         level,
450 | |                         "Failed to apply channel update: {:?}",
451 | |                         err
452 | |                     );
    | |_____________________^
    |
    = note: expected values for `feature` are: `criterion`, `default`, and `std`
    = help: consider adding `max_level_debug` as a feature in `Cargo.toml`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
    = note: this error originates in the macro `log_given_level` (in Nightly builds, run with -Z macro-backtrace for more info)
...
error: unexpected `cfg` condition value: `max_level_off`
   --> /workdir/rust-lightning/lightning-rapid-gossip-sync/src/processing.rs:466:3
    |
466 |         log_trace!(self.logger, "Done processing RGS data from {}", latest_seen_timestamp);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: expected values for `feature` are: `criterion`, `default`, and `std`
    = help: consider adding `max_level_off` as a feature in `Cargo.toml`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
    = note: this error originates in the macro `$crate::log_given_level` which comes from the expansion of the macro `log_trace` (in Nightly builds, run with -Z macro-backtrace for more info)
...

I'm able to work around this with the following patch:

diff --git a/lightning-rapid-gossip-sync/Cargo.toml b/lightning-rapid-gossip-sync/Cargo.toml
index 03efbde3..fb01aba8 100644
--- a/lightning-rapid-gossip-sync/Cargo.toml
+++ b/lightning-rapid-gossip-sync/Cargo.toml
@@ -12,6 +12,13 @@ Utility to process gossip routing data from Rapid Gossip Sync Server.
 [features]
 default = ["std"]
 std = ["bitcoin-io/std", "bitcoin_hashes/std"]
+max_level_off = []
+max_level_error = []
+max_level_warn = []
+max_level_info = []
+max_level_debug = []
+max_level_trace = []
+

 [dependencies]
 lightning = { version = "0.0.124", path = "../lightning", default-features = false }

[tnull]

Ah, thank you very much for reporting this issue! Should be fixed by #3425.

[tnull]

As discussed in #3425, we might want to solve this by simply dropping the max_level_* features as probably ~no user is really interested in limiting the maximum level at compile time.

@enigbe, would you be interested to pick this up as part of your logging work? Only caveat would be that we'd likely want to ship it as part of the next release, which might get cut end of next week.

[tnull]

Now opened #3431.

[enigbe]

Apologies for missing this earlier @tnull, but I've notice you've created #3431. I'll add a review shortly.