Invoke node directly in generate-specs.sh (#30781)

Summary:
Currently, Codegen bash wrapper (`generate-specs.sh`) for Xcode invokes JS-based Codegen tooling via `yarn --silent node <...>`. This breaks both:

- when Yarn is not installed (if NPM is used), for obvious reasons
- when Yarn v2 ("Berry") is active

This PR changes the way `generate-specs.sh` locates `node` executable to the following algorithm:

- use the path provided in the `NODE_BINARY` env var
- if `NODE_BINARY` env var is not defined, find `node` with `command -v node`

## Changelog

[iOS] [Fixed] - Fix Codegen silently failing when Yarn is not installed, or when Yarn v2 is active.

Pull Request resolved: #30781

Test Plan:
### Case 1 (no Yarn installed)

1. Ensure `yarn` is not present in PATH
2. Run Xcode build
3. Check that Codegen artifacts are produced

### Case 2 (Yarn v2 is used)

1. Ensure `yarn` is running in the v2 ("Berry") mode
2. Run Xcode build
3. Check that Codegen artifacts are produced

Reviewed By: fkgozali

Differential Revision: D26187081

Pulled By: hramos

fbshipit-source-id: 77d3089f523b8c976d8223b77ff9553cb6cf68a5

Author: ivanmoskalev

scripts/generate-specs.sh

@@ -27,7 +27,7 @@ set -e
 THIS_DIR=$(cd -P "$(dirname "$(readlink "${BASH_SOURCE[0]}" || echo "${BASH_SOURCE[0]}")")" && pwd)
 TEMP_DIR=$(mktemp -d /tmp/react-native-codegen-XXXXXXXX)
 RN_DIR=$(cd "$THIS_DIR/.." && pwd)
-YARN_BINARY="${YARN_BINARY:-$(command -v yarn || true)}"
+NODE_BINARY="${NODE_BINARY:-$(command -v node || true)}"
 USE_FABRIC="${USE_FABRIC:-0}"
 
 cleanup () {
@@ -56,8 +56,8 @@ main() {
   CODEGEN_REPO_PATH="$RN_DIR/packages/react-native-codegen"
   CODEGEN_NPM_PATH="$RN_DIR/../react-native-codegen"
 
-  if [ -z "$YARN_BINARY" ]; then
-    echo "Error: Could not find yarn. Make sure it is in bash PATH or set the YARN_BINARY environment variable." 1>&2
+if [ -z "$NODE_BINARY" ]; then
+    echo "Error: Could not find node. Make sure it is in bash PATH or set the NODE_BINARY environment variable." 1>&2
     exit 1
   fi
 
@@ -72,18 +72,20 @@ main() {
 
   if [ ! -d "$CODEGEN_PATH/lib" ]; then
     describe "Building react-native-codegen package"
-    pushd "$CODEGEN_PATH" >/dev/null || exit 1
-      "$YARN_BINARY"
-      "$YARN_BINARY" build
-    popd >/dev/null || exit 1
+    bash "$CODEGEN_PATH/scripts/oss/build.sh"
+  fi
+
+  if [ -z "$NODE_BINARY" ]; then
+    echo "Error: Could not find node. Make sure it is in bash PATH or set the NODE_BINARY environment variable." 1>&2
+    exit 1
   fi
 
   describe "Generating schema from flow types"
-  "$YARN_BINARY" node "$CODEGEN_PATH/lib/cli/combine/combine-js-to-schema-cli.js" "$SCHEMA_FILE" "$SRCS_DIR"
+  "$NODE_BINARY" "$CODEGEN_PATH/lib/cli/combine/combine-js-to-schema-cli.js" "$SCHEMA_FILE" "$SRCS_DIR"
 
   describe "Generating native code from schema (iOS)"
   pushd "$RN_DIR" >/dev/null || exit 1
-    "$YARN_BINARY" --silent node scripts/generate-specs-cli.js ios "$SCHEMA_FILE" "$TEMP_OUTPUT_DIR" "$CODEGEN_MODULES_LIBRARY_NAME"
+    "$NODE_BINARY" scripts/generate-specs-cli.js ios "$SCHEMA_FILE" "$TEMP_OUTPUT_DIR" "$CODEGEN_MODULES_LIBRARY_NAME"
   popd >/dev/null || exit 1
 
   describe "Copying output to final directory"