Avoid the use of #[cfg(doc)] in std_detect (#1283)

Co-authored-by: bjorn3 <bjorn3@users.noreply.github.com>

Author: Amanieu

crates/std_detect/src/detect/arch/aarch64.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: aarch64;
+    @CFG: target_arch = "aarch64";
     @MACRO_NAME: is_aarch64_feature_detected;
     @MACRO_ATTRS:
     /// This macro tests, at runtime, whether an `aarch64` feature is enabled on aarch64 platforms.

crates/std_detect/src/detect/arch/arm.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: arm;
+    @CFG: target_arch = "arm";
     @MACRO_NAME: is_arm_feature_detected;
     @MACRO_ATTRS:
     /// Checks if `arm` feature is enabled.

crates/std_detect/src/detect/arch/mips.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: mips;
+    @CFG: target_arch = "mips";
     @MACRO_NAME: is_mips_feature_detected;
     @MACRO_ATTRS:
     /// Checks if `mips` feature is enabled.

crates/std_detect/src/detect/arch/mips64.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: mips64;
+    @CFG: target_arch = "mips64";
     @MACRO_NAME: is_mips64_feature_detected;
     @MACRO_ATTRS:
     /// Checks if `mips64` feature is enabled.

crates/std_detect/src/detect/arch/mod.rs

@@ -0,0 +1,56 @@
+#![allow(dead_code)]
+
+use cfg_if::cfg_if;
+
+// Export the macros for all supported architectures.
+#[macro_use]
+mod x86;
+#[macro_use]
+mod arm;
+#[macro_use]
+mod aarch64;
+#[macro_use]
+mod riscv;
+#[macro_use]
+mod powerpc;
+#[macro_use]
+mod powerpc64;
+#[macro_use]
+mod mips;
+#[macro_use]
+mod mips64;
+
+cfg_if! {
+    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
+        pub use x86::*;
+    } else if #[cfg(target_arch = "arm")] {
+        pub use arm::*;
+    } else if #[cfg(target_arch = "aarch64")] {
+        pub use aarch64::*;
+    } else if #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))] {
+        pub use riscv::*;
+    } else if #[cfg(target_arch = "powerpc")] {
+        pub use powerpc::*;
+    } else if #[cfg(target_arch = "powerpc64")] {
+        pub use powerpc64::*;
+    } else if #[cfg(target_arch = "mips")] {
+        pub use mips::*;
+    } else if #[cfg(target_arch = "mips64")] {
+        pub use mips64::*;
+    } else {
+        // Unimplemented architecture:
+        #[doc(hidden)]
+        pub(crate) enum Feature {
+            Null
+        }
+        #[doc(hidden)]
+        pub mod __is_feature_detected {}
+
+        impl Feature {
+            #[doc(hidden)]
+            pub(crate) fn from_str(_s: &str) -> Result<Feature, ()> { Err(()) }
+            #[doc(hidden)]
+            pub(crate) fn to_str(self) -> &'static str { "" }
+        }
+    }
+}

crates/std_detect/src/detect/arch/powerpc.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: powerpc;
+    @CFG: target_arch = "powerpc";
     @MACRO_NAME: is_powerpc_feature_detected;
     @MACRO_ATTRS:
     /// Checks if `powerpc` feature is enabled.

crates/std_detect/src/detect/arch/powerpc64.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: powerpc64;
+    @CFG: target_arch = "powerpc64";
     @MACRO_NAME: is_powerpc64_feature_detected;
     @MACRO_ATTRS:
     /// Checks if `powerpc` feature is enabled.

crates/std_detect/src/detect/arch/riscv.rs

@@ -2,6 +2,7 @@
 
 features! {
     @TARGET: riscv;
+    @CFG: any(target_arch = "riscv32", target_arch = "riscv64");
     @MACRO_NAME: is_riscv_feature_detected;
     @MACRO_ATTRS:
     /// A macro to test at *runtime* whether instruction sets are available on

crates/std_detect/src/detect/arch/x86.rs

@@ -17,6 +17,7 @@
 
 features! {
     @TARGET: x86;
+    @CFG: any(target_arch = "x86", target_arch = "x86_64");
     @MACRO_NAME: is_x86_feature_detected;
     @MACRO_ATTRS:
     /// A macro to test at *runtime* whether a CPU feature is available on