Re-apply: Consider relative to pwd installation root when looking for files in rn module via cocoapods (facebook#33427)

Summary:
This re-applies Consider relative to pwd installation root when looking for files in rn module via cocoapods by danilobuerger

The `:reactNativePath` provided by `use_native_modules!` is the rn module path relative to the installation root (usually `./ios`). However, when executing cocoapods from a dir thats not the installation root, packages that use the relative `:reactNativePath` variable in their path must also consider the relative to pwd installation root.

This fixes usage of cocoapods with the `--project-directory` flag like

```bash
bundle exec pod install --project-directory=ios
```
## Changelog

[iOS] [Fixed] - Fix usage of cocoapods with --project-directory flag and new arch

Pull Request resolved: facebook#33427

Test Plan:
1) Enable the new arch
2) Execute from the projects root dir

```bash
bundle exec pod install --project-directory=ios
```

3) It will fail with

```
[!] Invalid `Podfile` file: [codegen] Couldn't not find react-native-codegen..
```

4) Apply the patch
5) Execute from the projects root dir

```bash
bundle exec pod install --project-directory=ios
```

6) It will succeed

Reviewed By: cortinico

Differential Revision: D34890926

Pulled By: dmitryrykun

fbshipit-source-id: f7adc6196874822d5ff38f275414f529d385f2ea

Author: danilobuerger

scripts/react_native_pods.rb

@@ -281,8 +281,9 @@ def modify_flags_for_new_architecture(installer, cpp_flags)
 end
 
 def build_codegen!(react_native_path)
-  codegen_repo_path = "#{react_native_path}/packages/react-native-codegen";
-  codegen_npm_path = "#{react_native_path}/../react-native-codegen";
+  relative_installation_root = Pod::Config.instance.installation_root.relative_path_from(Pathname.pwd)
+  codegen_repo_path = "#{relative_installation_root}/#{react_native_path}/packages/react-native-codegen";
+  codegen_npm_path = "#{relative_installation_root}/#{react_native_path}/../react-native-codegen";
   codegen_cli_path = ""
   if Dir.exist?(codegen_repo_path)
     codegen_cli_path = codegen_repo_path
@@ -323,7 +324,7 @@ def checkAndGenerateEmptyThirdPartyProvider!(react_native_path)
     Pod::Executable.execute_command(
       'node',
       [
-        "#{react_native_path}/scripts/generate-provider-cli.js",
+        "#{relative_installation_root}/#{react_native_path}/scripts/generate-provider-cli.js",
         "--platform", 'ios',
         "--schemaListPath", temp_schema_list_path,
         "--outputDir", "#{output_dir}"
@@ -514,6 +515,7 @@ def use_react_native_codegen_discovery!(options={})
   app_path = options[:app_path]
   fabric_enabled = options[:fabric_enabled] ||= false
   config_file_dir = options[:config_file_dir] ||= ''
+  relative_installation_root = Pod::Config.instance.installation_root.relative_path_from(Pathname.pwd)
 
   if !app_path
     Pod::UI.warn '[Codegen] Error: app_path is required for use_react_native_codegen_discovery.'
@@ -529,7 +531,7 @@ def use_react_native_codegen_discovery!(options={})
   out = Pod::Executable.execute_command(
     'node',
     [
-      "#{react_native_path}/scripts/generate-artifacts.js",
+      "#{relative_installation_root}/#{react_native_path}/scripts/generate-artifacts.js",
       "-p", "#{app_path}",
       "-o", Pod::Config.instance.installation_root,
       "-e", "#{fabric_enabled}",

template/ios/Podfile

@@ -15,8 +15,8 @@ target 'HelloWorld' do
     # to enable hermes on iOS, change `false` to `true` and then install pods
     :hermes_enabled => flags[:hermes_enabled],
     :fabric_enabled => flags[:fabric_enabled],
-    # An abosolute path to your application root.
-    :app_path => "#{Dir.pwd}/.."
+    # An absolute path to your application root.
+    :app_path => "#{Pod::Config.instance.installation_root}/.."
   )
 
   target 'HelloWorldTests' do