yarn-berry-fetchers: Allow impure env vars (#522626)

pkgs/by-name/ya/yarn-berry/fetcher/fetch-yarn-berry-deps.nix

@@ -47,6 +47,8 @@ stdenv.mkDerivation (
       cacert
     ];
 
+    impureEnvVars = lib.fetchers.proxyImpureEnvVars;
+
     buildPhase = ''
       runHook preBuild
 

pkgs/by-name/ya/yarn-berry/fetcher/yarn-berry-fetcher.nix

@@ -28,6 +28,8 @@ rustPlatform.buildRustPackage (finalAttrs: {
   env.YARN_ZIP_SUPPORTED_CACHE_VERSION = berryCacheVersion;
   env.LIBZIP_SYS_USE_PKG_CONFIG = 1;
 
+  impureEnvVars = lib.fetchers.proxyImpureEnvVars;
+
   nativeBuildInputs = [
     rustPlatform.bindgenHook
     pkg-config