Fix compilation issues with -Zminimum-versions

This does not affect the code and only means we
declare more specific versions in Cargo.toml.

Fixes #357

Author: Techcable

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - **[Fix]** Restore compatibility with `erased-serde` version `0.3`.
   - Compatibility with `erased-serde` version `0.4` may be provided again in a
     future version.
+* Ensure compatibility with `-Zminimal-versions` flag by specifying minimal dependency versions (fixes #357)
+  - Not (yet) tested in CI
 
 ## [2.8.0] - 2025-10-05
 This is the biggest slog release since 2.0. It fully preserves compatibility with prior releases.

Cargo.toml

@@ -118,16 +118,18 @@ default-features = false
 features = ["alloc"]  # erased-serde always requires alloc, and so does slog
 
 [build-dependencies]
-rustversion = "1"
+# rustversion v1.0.6 added the rustversion::cfg! macro
+rustversion = "1.0.6"
 
 [dev-dependencies]
 # NOTE: This is just a macro (not a runtime dependency)
 #
 # It is used to conditionally enable use of newer rust language
 # features depending on the compiler features.
-rustversion = "1"
-serde = "1"
-serde_derive = "1"
+rustversion = "1.0.6"
+# first version to support serde_core
+serde = "1.0.220"
+serde_derive = "1.0.220"
 
 [[example]]
 name = "singlethread"