Update portable-simd

This avoids building wasm-bindgen-test on non-wasm targets, reducing
test time.

Author: bjorn3

build_system/tests.rs

@@ -109,7 +109,7 @@ pub(crate) static REGEX: CargoProject = CargoProject::new(&REGEX_REPO.source_dir
 pub(crate) static PORTABLE_SIMD_REPO: GitRepo = GitRepo::github(
     "rust-lang",
     "portable-simd",
-    "9bd30e77b3a3c699af102ebb3df0f6110f8aa02e",
+    "e6bbf49ba91d1ad058c7184cfc34b1c2ca6ef64d",
     "portable-simd",
 );