Bazel build inside nix flake fails: 'python3: No such file or directory

[SpamDoodler]

I trying to compile cpp to webassambly using bazel.
bazel build //:add_wasm
fails with:

...
env: 'python3': No such file or directory
...

flake.nix

{
  description = "Nix flake";
  
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };
  
  outputs = { self, nixpkgs, flake-utils }: 
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs { inherit system; };
      in
      {
        devShells.default = pkgs.mkShell {
          name = "wasm-dev";
          EM_CONFIG = pkgs.writeText ".emscripten" ''
            EMSCRIPTEN_ROOT = '${pkgs.emscripten}/share/emscripten'
            LLVM_ROOT = '${pkgs.emscripten.llvmEnv}/bin'
            BINARYEN_ROOT = '${pkgs.binaryen}'
            NODE_JS = '${pkgs.nodejs}/bin/node'
            CACHE = '${toString ./.cache}'
          '';
          buildInputs = with pkgs; [
            clang_21          
            lld_21             
            emscripten
            nodejs
            yarn
            bazel
            python313Full
            python313Packages.pip
          ];
          
          shellHook = ''
            export PATH=${pkgs.python3Full}/bin:$PATH
            export PYTHON=python3 
            export PYTHON_BIN_PATH=${pkgs.python3Full}/bin/python3

            # Initialize emscripten config if needed (first run)
            if [ ! -f "$HOME/.emscripten" ]; then
              echo "Initializing Emscripten configuration..."
              emcc --version > /dev/null 2>&1
            fi
          '';
        };
      }
    );

MODULE.bazel

bazel_version = "7.6.0"

module(
    name = "polyglot_wasm",
    version = "0.1.0",
)

bazel_dep(name = "emsdk", version = "4.0.13")
bazel_dep(name = "rules_rust", version = "0.64.0")
bazel_dep(name = "rules_python", version = "0.31.0")

python = use_extension("@rules_python//python/extensions:python.bzl", "python")
python.toolchain(
    python_version = "3.13",
)
use_repo(python, "python_3_13")

git_override(
    module_name = "emsdk",
    remote = "https://github.com/emscripten-core/emsdk.git",
    strip_prefix = "bazel",
    commit = "eff90ca04a3785f571a8095b3a42b63799cf384a",
)

emscripten_deps = use_extension(
    "@emsdk//:emscripten_deps.bzl",
    "emscripten_deps",
)

BUILD

load("@rules_cc//cc:defs.bzl", "cc_binary")
load("@emsdk//emscripten_toolchain:wasm_rules.bzl", "wasm_cc_binary")

cc_binary(
    name = "add",
    srcs = ["hello.c"],
    linkopts = [
        "-s", "EXPORTED_FUNCTIONS=['_main']",
        "-s", "EXPORTED_RUNTIME_METHODS=['ccall','cwrap']",
    ],  
)

wasm_cc_binary(
    name = "add_wasm",
    cc_target = ":add",
)

.bazelrc

build --incompatible_enable_cc_toolchain_resolution
build --platforms=@emsdk//:platform_wasm
build --extra_toolchains=@emsdk//:all

$> which python3
/nix/store/0n3p6v273rh7g1ypbfc0vwlw1sw79y1p-python3-3.13.6/bin/python3