Add doc_cfg for annotations on nightly

Signed-off-by: Joe Richey <joerichey@google.com>

Cargo.toml

@@ -37,10 +37,11 @@ cc = { version = "1.0.37", optional = true }
 default = [ "nightly", "instructions" ]
 instructions = []
 external_asm = [ "cc" ]
-nightly = [ "inline_asm", "const_fn", "abi_x86_interrupt" ]
+nightly = [ "inline_asm", "const_fn", "abi_x86_interrupt", "doc_cfg" ]
 inline_asm = []
 abi_x86_interrupt = []
 const_fn = []
+doc_cfg = []
 
 [package.metadata.release]
 no-dev-version = true

src/instructions/interrupts.rs

@@ -153,7 +153,10 @@ pub fn int3() {
 /// immediate. This macro will be replaced by a generic function when support for
 /// const generics is implemented in Rust.
 #[cfg(feature = "inline_asm")]
-#[cfg_attr(docsrs, doc(cfg(any(feature = "nightly", feature = "inline_asm"))))]
+#[cfg_attr(
+    feature = "doc_cfg",
+    doc(cfg(any(feature = "nightly", feature = "inline_asm")))
+)]
 #[macro_export]
 macro_rules! software_interrupt {
     ($x:expr) => {{

src/instructions/mod.rs

@@ -54,7 +54,10 @@ pub fn bochs_breakpoint() {
 /// Gets the current instruction pointer. Note that this is only approximate as it requires a few
 /// instructions to execute.
 #[cfg(feature = "inline_asm")]
-#[cfg_attr(docsrs, doc(cfg(any(feature = "nightly", feature = "inline_asm"))))]
+#[cfg_attr(
+    feature = "doc_cfg",
+    doc(cfg(any(feature = "nightly", feature = "inline_asm")))
+)]
 #[inline(always)]
 pub fn read_rip() -> crate::VirtAddr {
     let rip: u64;

src/lib.rs

@@ -8,7 +8,7 @@
 #![cfg_attr(feature = "const_fn", feature(const_fn_trait_bound))] // PageSize marker trait
 #![cfg_attr(feature = "inline_asm", feature(asm))]
 #![cfg_attr(feature = "abi_x86_interrupt", feature(abi_x86_interrupt))]
-#![cfg_attr(docsrs, feature(doc_cfg))]
+#![cfg_attr(feature = "doc_cfg", feature(doc_cfg))]
 #![warn(missing_docs)]
 #![deny(missing_debug_implementations)]