Support recursive symlinks in release script

See
https://github.com/cdr/code-server/issues/1746#issuecomment-637830396

ci/build/code-server.sh

@@ -1,26 +1,40 @@
 #!/bin/sh
+set -eu
 
 # This script is intended to be bundled into the standalone releases.
 # Runs code-server with the bundled node binary.
 
-# More complicated than readlink -f or realpath to support macOS.
-# See https://github.com/cdr/code-server/issues/1537
-root_dir() {
-  # We read the symlink, which may be relative from $0.
-  dst="$(readlink "$0")"
-  # We cd into the $0 directory.
-  cd "$(dirname "$0")" || exit 1
-  # Now we can cd into the directory above the dst directory which is the root
-  # of the release.
-  cd "$(dirname "$dst")/.." || exit 1
-  # Finally we use pwd -P to print the absolute path the root.
-  pwd -P || exit 1
+_realpath() {
+  if [ "$(uname)" = "Linux" ]; then
+    readlink -f "$1"
+    return
+  fi
+
+  # See https://github.com/cdr/code-server/issues/1537
+  if [ "$(uname)" = "Darwin" ]; then
+    # We read the symlink, which may be relative from $1.
+    script="$1"
+    if [ -L "$script" ]; then
+      while [ -L "$script" ]; do
+        script="$(readlink "$script")"
+        cd "$(dirname "$script")"
+      done
+    else
+      cd "$(dirname "$script")"
+    fi
+
+    echo "$PWD/$(basename "$script")"
+    return
+  fi
+
+  echo "Unsupported OS $(uname)" >&2
+  exit 1
 }
 
-ROOT="$(root_dir)"
+ROOT="$(dirname "$(dirname "$(_realpath "$0")")")"
 if [ "$(uname)" = "Linux" ]; then
-  export LD_LIBRARY_PATH="$ROOT/lib:$LD_LIBRARY_PATH"
+  export LD_LIBRARY_PATH="$ROOT/lib:${LD_LIBRARY_PATH-}"
 elif [ "$(uname)" = "Darwin" ]; then
-  export DYLD_LIBRARY_PATH="$ROOT/lib:$DYLD_LIBRARY_PATH"
+  export DYLD_LIBRARY_PATH="$ROOT/lib:${DYLD_LIBRARY_PATH-}"
 fi
 exec "$ROOT/lib/node" "$ROOT" "$@"