std: only depend on dlmalloc for wasm*-unknown

It was already filtered out for emscripten, but wasi doesn't need dlmalloc
either since it reuses `unix/alloc.rs`.

Author: cuviper

library/std/Cargo.toml

@@ -38,7 +38,7 @@ features = ['read_core', 'elf', 'macho', 'pe', 'unaligned', 'archive']
 rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
 rand_xorshift = "0.3.0"
 
-[target.'cfg(any(all(target_family = "wasm", not(target_os = "emscripten")), all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
+[target.'cfg(any(all(target_family = "wasm", target_os = "unknown"), all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
 dlmalloc = { version = "0.2.3", features = ['rustc-dep-of-std'] }
 
 [target.x86_64-fortanix-unknown-sgx.dependencies]