Update stdarch submodule (to before it switched to const generics)

This also includes a cherry-pick of
rust-lang/stdarch@ec14619
and rust-lang/stdarch#1108 to fix a build
failure.

It also adds a re-export of various macros to the crate root of libstd -
previously they would show up automatically because std_detect was defined
in the same crate.

Author: jyn514

std/Cargo.toml

@@ -21,6 +21,7 @@ compiler_builtins = { version = "0.1.39" }
 profiler_builtins = { path = "../profiler_builtins", optional = true }
 unwind = { path = "../unwind" }
 hashbrown = { version = "0.11", default-features = false, features = ['rustc-dep-of-std'] }
+std_detect = { path = "../stdarch/crates/std_detect", default-features = false, features = ['rustc-dep-of-std'] }
 
 # Dependencies of the `backtrace` crate
 addr2line = { version = "0.14.0", optional = true, default-features = false }
@@ -70,8 +71,8 @@ panic_immediate_abort = ["core/panic_immediate_abort"]
 
 # Enable std_detect default features for stdarch/crates/std_detect:
 # https://github.com/rust-lang/stdarch/blob/master/crates/std_detect/Cargo.toml
-std_detect_file_io = []
-std_detect_dlsym_getauxval = []
+std_detect_file_io = ["std_detect/std_detect_file_io"]
+std_detect_dlsym_getauxval = ["std_detect/std_detect_dlsym_getauxval"]
 
 [package.metadata.fortanix-sgx]
 # Maximum possible number of threads when testing

std/src/lib.rs

@@ -539,22 +539,16 @@ pub mod rt;
 #[allow(dead_code, unused_attributes)]
 mod backtrace_rs;
 
-// Pull in the `std_detect` crate directly into libstd. The contents of
-// `std_detect` are in a different repository: rust-lang/stdarch.
-//
-// `std_detect` depends on libstd, but the contents of this module are
-// set up in such a way that directly pulling it here works such that the
-// crate uses the this crate as its libstd.
-#[path = "../../stdarch/crates/std_detect/src/mod.rs"]
-#[allow(missing_debug_implementations, missing_docs, dead_code)]
-#[unstable(feature = "stdsimd", issue = "48556")]
-#[cfg(not(test))]
-mod std_detect;
-
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub use std_detect::is_x86_feature_detected;
 #[doc(hidden)]
 #[unstable(feature = "stdsimd", issue = "48556")]
-#[cfg(not(test))]
-pub use std_detect::detect;
+pub use std_detect::*;
+#[unstable(feature = "stdsimd", issue = "48556")]
+pub use std_detect::{
+    is_aarch64_feature_detected, is_arm_feature_detected, is_mips64_feature_detected,
+    is_mips_feature_detected, is_powerpc64_feature_detected, is_powerpc_feature_detected,
+};
 
 // Re-export macros defined in libcore.
 #[stable(feature = "rust1", since = "1.0.0")]

stdarch

@@ -1 +1 @@
-Subproject commit 9c732a56f67f54d12a0b4fd99993154906c95ea6
+Subproject commit 19f5459dd0f89e466b7bcaa0f69ecca90f21a4d1