Rollup merge of rust-lang#125296 - tesuji:checkcfg-buildstd, r=Nilstrieb,michaelwoerister

Fix `unexpected_cfgs` lint on std

closes rust-lang#125291

r? rust-lang/compiler

Author: fmease

alloc/Cargo.toml

@@ -40,3 +40,15 @@ compiler-builtins-weak-intrinsics = ["compiler_builtins/weak-intrinsics"]
 panic_immediate_abort = ["core/panic_immediate_abort"]
 # Choose algorithms that are optimized for binary size instead of runtime performance
 optimize_for_size = ["core/optimize_for_size"]
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+# x.py uses beta cargo, so `check-cfg` entries do not yet take effect
+# for rust-lang/rust. But for users of `-Zbuild-std` it does.
+# The unused warning is waiting for rust-lang/cargo#13925 to reach beta.
+check-cfg = [
+    'cfg(bootstrap)',
+    'cfg(no_global_oom_handling)',
+    'cfg(no_rc)',
+    'cfg(no_sync)',
+]

core/Cargo.toml

@@ -36,3 +36,16 @@ optimize_for_size = []
 # Make `RefCell` store additional debugging information, which is printed out when
 # a borrow error occurs
 debug_refcell = []
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+# x.py uses beta cargo, so `check-cfg` entries do not yet take effect
+# for rust-lang/rust. But for users of `-Zbuild-std` it does.
+# The unused warning is waiting for rust-lang/cargo#13925 to reach beta.
+check-cfg = [
+    'cfg(bootstrap)',
+    'cfg(no_fp_fmt_parse)',
+    'cfg(stdarch_intel_sde)',
+    # This matches `EXTRA_CHECK_CFGS` in `src/bootstrap/src/lib.rs`.
+    'cfg(feature, values(any()))',
+]

std/Cargo.toml

@@ -97,3 +97,13 @@ heap_size = 0x8000000
 name = "stdbenches"
 path = "benches/lib.rs"
 test = true
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    'cfg(bootstrap)',
+    'cfg(backtrace_in_libstd)',
+    'cfg(netbsd10)',
+    'cfg(target_arch, values("xtensa"))',
+    'cfg(feature, values("std", "as_crate"))',
+]