Fixing MSRV-breaking dependencies

Cargo.toml

@@ -57,9 +57,24 @@ paste = "1.0.8"
 rand = "0.9.0"
 rand_chacha = "0.9.0"
 criterion = "0.5"
+# Note: `half` v2.5.0 started to require Rust 1.81.
+# `criterion` transitively depends on `half` via the dependency chain:
+#     criterion -> ciborium -> ciborium_ll -> half
+# The MSRV of `ciborium` v0.2.2 is declared as 1.58, and is declared to depend on `half` v2.2.
+# Ciborium should either bump its MSRV or select a version of `half` that satisfies its current MSRV.
+# We lock the version of `half` to 2.4.1 to workaround this.
+# TODO: When we bump MSRV to 1.84 or above, we can rely on Cargo's MSRV-aware dependency resolver and remove such workarounds.
+half = "=2.4.1"
 
 [build-dependencies]
 built = { version = "0.7.7", features = ["git2"] }
+# Note: Some components in ICU4X started to require Rust 1.81 since some versions, such as `litemap` v0.7.5.
+# The `built` crate depends on ICU4X via the dependency chain:
+#     built -> git2 -> url -> idna -> idna_adapter --(default)--------> crates from the ICU4X projects
+#                                                  --(alternatively)--> `unicode-rs`
+# But we don't need ICU4X (or even `url`) because we only use `git2` to get the Git commit hash.
+# We move away from ICU4X completely following the instruction in https://docs.rs/crate/idna_adapter/1.2.0
+idna_adapter = "=1.1.0"
 
 [[bench]]
 name = "main"