envoy: fix up Rust builds

This unblocks using wasmtime rather than wamr as the WASM runtime in
envoy (see NixOS#425065).

Author: lukegb

pkgs/by-name/en/envoy/bazel_nix.BUILD.bazel

@@ -1,12 +1,26 @@
 load("@bazel_tools//tools/sh:sh_toolchain.bzl", "sh_toolchain")
 load("@rules_rust//rust:toolchain.bzl", "rust_toolchain")
+load("@rules_rust//rust:defs.bzl", "rust_stdlib_filegroup")
 
 toolchains = {
     "x86_64": "x86_64-unknown-linux-gnu",
     "aarch64": "aarch64-unknown-linux-gnu",
 }
 
-exports_files(["cargo", "rustdoc", "ruststd", "rustc"])
+exports_files(["cargo", "rustdoc", "rustc"])
+
+[
+    rust_stdlib_filegroup(
+        name = "rust_nix_" + k + "_stdlib",
+        srcs = glob(
+            [
+                "rustcroot/lib/rustlib/" + v + "/lib/**",
+            ],
+            allow_empty=True,
+        ),
+    )
+    for k, v in toolchains.items()
+]
 
 [
     rust_toolchain(
@@ -16,7 +30,7 @@ exports_files(["cargo", "rustdoc", "ruststd", "rustc"])
         exec_triple = v,
         cargo = ":cargo",
         rust_doc = ":rustdoc",
-        rust_std = ":ruststd",
+        rust_std = ":rust_nix_" + k + "_stdlib",
         rustc = ":rustc",
         stdlib_linkflags = ["-ldl", "-lpthread"],
         staticlib_ext = ".a",

pkgs/by-name/en/envoy/package.nix

@@ -94,7 +94,7 @@ buildBazelPackage rec {
     ln -sf "${cargo}/bin/cargo" bazel/nix/cargo
     ln -sf "${rustc}/bin/rustc" bazel/nix/rustc
     ln -sf "${rustc}/bin/rustdoc" bazel/nix/rustdoc
-    ln -sf "${rustPlatform.rustLibSrc}" bazel/nix/ruststd
+    ln -sf "${rustc.unwrapped}" bazel/nix/rustcroot
     substituteInPlace bazel/dependency_imports.bzl \
       --replace-fail 'crate_universe_dependencies()' 'crate_universe_dependencies(rust_toolchain_cargo_template="@@//bazel/nix:cargo", rust_toolchain_rustc_template="@@//bazel/nix:rustc")' \
       --replace-fail 'crates_repository(' 'crates_repository(rust_toolchain_cargo_template="@@//bazel/nix:cargo", rust_toolchain_rustc_template="@@//bazel/nix:rustc",'
@@ -239,6 +239,7 @@ buildBazelPackage rec {
     "--linkopt=-Wl,-z,noexecstack"
     "--config=gcc"
     "--verbose_failures"
+    "--incompatible_enable_cc_toolchain_resolution=true"
 
     # Force use of system Java.
     "--extra_toolchains=@local_jdk//:all"