wasmtime: init and use for emulation

This isn’t really an "emulator" but it’s the closest concept we have
right now.

lib/systems/default.nix

@@ -115,8 +115,8 @@ rec {
         then "${wine}/bin/${wine-name}"
         else if final.isLinux && pkgs.stdenv.hostPlatform.isLinux
         then "${qemu-user}/bin/qemu-${final.qemuArch}"
-        else if final.isWasm
-        then "${pkgs.v8}/bin/d8"
+        else if final.isWasi
+        then "${pkgs.wasmtime}/bin/wasmtime"
         else throw "Don't know how to run ${final.config} executables.";
 
     } // mapAttrs (n: v: v final.parsed) inspect.predicates

pkgs/development/interpreters/wasmtime/default.nix

@@ -0,0 +1,31 @@
+{ rustPlatform, fetchFromGitHub, lib, python, cmake, llvmPackages, clang }:
+
+rustPlatform.buildRustPackage rec {
+  name = "wasmtime-${version}";
+  version = "0.1.0";
+
+  src = fetchFromGitHub {
+    owner = "CraneStation";
+    repo = "wasmtime";
+    rev = "07a6ca8f4e1136ecd9f4af8d1f03a01aade60407";
+    sha256 = "1cq6nz90kaf023mcyblca90bpvbzhq8xjq01laa28v7r50lagcn5";
+    fetchSubmodules = true;
+  };
+
+  cargoSha256 = "17k8n5xar4pvvi4prhm6c51vlim9xqwkkhysbnss299mm3fyh36h";
+
+  cargoPatches = [ ./cargo-lock.patch ];
+
+  nativeBuildInputs = [ python cmake clang ];
+  buildInputs = [ llvmPackages.libclang ];
+
+  LIBCLANG_PATH = "${llvmPackages.libclang}/lib";
+
+  meta = with lib; {
+    description = "Standalone JIT-style runtime for WebAsssembly, using Cranelift";
+    homepage = https://github.com/CraneStation/wasmtime;
+    license = licenses.asl20;
+    maintainers = [ maintainers.matthewbauer ];
+    platforms = platforms.unix;
+  };
+}

pkgs/top-level/all-packages.nix

@@ -23815,4 +23815,6 @@ in
     stdenv = crossLibcStdenv;
   };
 
+  wasmtime = callPackage ../development/interpreters/wasmtime {};
+
 }