Remove unused "mem" feature

hermit-sys/build.rs

@@ -153,13 +153,6 @@ fn build_hermit(src_dir: &Path, target_dir_opt: Option<&Path>) {
 	rename_symbol("rust_begin_unwind", &lib);
 	rename_symbol("rust_oom", &lib);
 
-	#[cfg(feature = "mem")]
-	{
-		for symbol in ["memcpy", "memmove", "memset", "memcmp", "bcmp"] {
-			rename_symbol(symbol, &lib);
-		}
-	}
-
 	println!("cargo:rustc-link-search=native={}", lib_location.display());
 	println!("cargo:rustc-link-lib=static=hermit");
 
@@ -169,8 +162,6 @@ fn build_hermit(src_dir: &Path, target_dir_opt: Option<&Path>) {
 
 /// Kernel and user space has its own versions of panic handler, oom handler, memcpy, memset, etc,
 /// Consequently, we rename the functions in the libos to avoid collisions.
-/// In addition, it provides us the offer to create a optimized version of memcpy
-/// in user space.
 fn rename_symbol(symbol: impl AsRef<OsStr>, lib: impl AsRef<Path>) {
 	let arg = IntoIterator::into_iter([symbol.as_ref(), "=kernel-".as_ref(), symbol.as_ref()])
 		.collect::<OsString>();