RNGP - Pass PROJECT_ROOT_DIR to CMake (facebook#46958)

Summary:
Pull Request resolved: facebook#46958

This will make it easier to link against custom C++ TM which will most likely live inside ./shared or
some other paths outside of ./android.

CMake will have access to `PROJECT_ROOT_DIR` which points to ./android (the folder where the settings.gradle file exists).

Changelog:
[Internal] [Changed] - RNGP - Pass PROJECT_ROOT_DIR to CMake

Reviewed By: cipolleschi

Differential Revision: D64183641

fbshipit-source-id: 347256c04f10e92cf5a13e9c70db16aa29bcb741

packages/gradle-plugin/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/utils/NdkConfiguratorUtils.kt

@@ -43,6 +43,9 @@ internal object NdkConfiguratorUtils {
         if (cmakeArgs.none { it.startsWith("-DPROJECT_BUILD_DIR") }) {
           cmakeArgs.add("-DPROJECT_BUILD_DIR=${project.layout.buildDirectory.get().asFile}")
         }
+        if (cmakeArgs.none { it.startsWith("-DPROJECT_ROOT_DIR") }) {
+          cmakeArgs.add("-DPROJECT_ROOT_DIR=${project.rootProject.layout.projectDirectory.asFile}")
+        }
         if (cmakeArgs.none { it.startsWith("-DREACT_ANDROID_DIR") }) {
           cmakeArgs.add(
               "-DREACT_ANDROID_DIR=${extension.reactNativeDir.file("ReactAndroid").get().asFile}")