build: Ignore missing features in tests crates

tests-2018/Cargo.toml

@@ -18,6 +18,9 @@ path = "../tests/src/lib.rs"
 default = ["std"]
 std = []
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(feature, values("edition-2015"))'] }
+
 [dependencies]
 anyhow = "1.0.1"
 bytes = "1"

tests-no-std/Cargo.toml

@@ -11,6 +11,9 @@ build = "../tests/src/build.rs"
 doctest = false
 path = "../tests/src/lib.rs"
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(feature, values("edition-2015", "std"))'] }
+
 # Compile the `tests` crate *without* the std feature, which is implicitly
 # omitted from the default crate features. It would be easier to do something
 # like `cargo test -p tests --no-default-features`, but that currently does not

tests/Cargo.toml

@@ -11,6 +11,9 @@ build = "src/build.rs"
 default = ["std"]
 std = []
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(feature, values("edition-2015"))'] }
+
 [dependencies]
 anyhow = "1.0.1"
 cfg-if = "1"