swiftshader: fix build on hydra (#337213)

pkgs/development/libraries/swiftshader/default.nix

···
   src = fetchgit {
     url = "https://swiftshader.googlesource.com/SwiftShader";
     rev = "4e40d502c440cc59b25fa3a5fee0eadbab7442aa";
-    sha256 = "085bdqn80s7zw5h2pz6xff3j34hmkxb9wxzgjmzdr9c24zwp2k1c";
+    hash = "sha256-YtbTaOkFhVMKdu3jiRHQsPmoEu3KDzIQXLZ5HFBSmWI=";
+    # Remove 1GB of test files to get under Hydra output limit
+    postFetch = ''
+      rm -r $out/third_party/llvm-project/llvm/test
+      rm -r $out/third_party/json/test
+      rm -r $out/third_party/cppdap/third_party/json/test
+      rm -r $out/third_party/llvm-project/clang/test
+    '';
   };
 
   nativeBuildInputs = [ cmake python3 jq ];