VSX are pointless on Darwin. Also, mrustc cannot parse these modules.

diff --git a/library/stdarch/crates/core_arch/src/powerpc/mod.rs b/library/stdarch/crates/core_arch/src/powerpc/mod.rs
index 1234567..abcdefg 100644
--- a/library/stdarch/crates/core_arch/src/powerpc/mod.rs
+++ b/library/stdarch/crates/core_arch/src/powerpc/mod.rs
@@ -2,11 +2,16 @@
 
 pub(crate) mod macros;
 
+/// These modules fail to compile atm, disable them.
+#[cfg(target_feature = "altivec")]
 mod altivec;
+#[cfg(target_feature = "altivec")]
 #[unstable(feature = "stdarch_powerpc", issue = "111145")]
 pub use self::altivec::*;
 
+#[cfg(target_feature = "vsx")]
 mod vsx;
+#[cfg(target_feature = "vsx")]
 #[unstable(feature = "stdarch_powerpc", issue = "111145")]
 pub use self::vsx::*;
 
diff --git a/library/portable-simd/crates/core_simd/src/vendor.rs b/library/portable-simd/crates/core_simd/src/vendor.rs
index 1234567..abcdefg 100644
--- a/library/portable-simd/crates/core_simd/src/vendor.rs
+++ b/library/portable-simd/crates/core_simd/src/vendor.rs
@@ -10,6 +10,6 @@ mod wasm;
 #[cfg(any(target_arch = "aarch64", target_arch = "arm64ec", all(target_arch = "arm", target_feature = "v7")))]
 mod arm;

-#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
+#[cfg(all(any(target_arch = "powerpc", target_arch = "powerpc64"), target_feature = "vsx"))]
 mod powerpc;