yarn2nix: don't check for broken symlinks

Yarn seems to create a bunch of those, and we can't control Yarn.

pkgs/development/tools/yarn2nix-moretea/default.nix

@@ -162,6 +162,8 @@ in rec {
 
         runHook postBuild
       '';
+
+      dontCheckForBrokenSymlinks = true;
     };
 
   # This can be used as a shellHook in mkYarnPackage. It brings the built node_modules into
@@ -374,6 +376,8 @@ in rec {
         runHook postInstall
       '';
 
+      dontCheckForBrokenSymlinks = true;
+
       doDist = attrs.doDist or true;
 
       distPhase = attrs.distPhase or ''