nodejs: use a response file with llvm-ar

nodejs produces a static archive in its `postInstall`. It detects if the
`ar` is GNU ar and uses a response file. Otherwise, it adds the files
individually. This is apparently very slow with `llvm-ar`, which Darwin
now uses by default. Fortunately, `llvm-ar` also supports response
files, so detect whether the `ar` is `llvm-ar` and use a response file.

I tested the build on aarch64-darwin. `postInstall` took less than a
minute to generate a 59 MiB static archive. Comparing to the build on
master, the only difference between the two archives is `llvm-ar` zeroes
out the dates, uids, and gids by default. Compared disassembly of the
archives appeared identical.

This fixes the timeouts on staging-next. #241951

https://hydra.nixos.org/build/227170390

pkgs/development/web/nodejs/nodejs.nix

@@ -160,9 +160,14 @@ let
       ${if stdenv.buildPlatform.isGnu then ''
         ar -cqs $libv8/lib/libv8.a @files
       '' else ''
-        cat files | while read -r file; do
-          ar -cqS $libv8/lib/libv8.a $file
-        done
+        # llvm-ar supports response files, so take advantage of it if it’s available.
+        if [ "$(basename $(readlink -f $(command -v ar)))" = "llvm-ar" ]; then
+          ar -cqs $libv8/lib/libv8.a @files
+        else
+          cat files | while read -r file; do
+            ar -cqS $libv8/lib/libv8.a $file
+          done
+        fi
       ''}
       popd