Update CMakeLists.txt to resolve "react-native"

This enables end-users to build the iOS XCFramework locally from our npm package, if they need it built with the same version of Xcode as they're using to build their app.

src/jsi/CMakeLists.txt

@@ -1,5 +1,14 @@
-set(REACT_NATIVE_ROOT_DIR "${PACKAGE_ROOT_DIR}/node_modules/react-native")
+# Using Node.js to resolve the path to the "react-native" package.
+# This enables building for iOS on the end-users machine,
+# where "react-native" is installed as a sibling to our package instead of being a dev-dependency of our package.
+
+execute_process(
+    COMMAND node --print "path.dirname(require.resolve('react-native/package.json'))"
+    OUTPUT_VARIABLE REACT_NATIVE_ROOT_DIR
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+)
 set(JSI_HEADER_DIR "${REACT_NATIVE_ROOT_DIR}/ReactCommon/jsi")
+message(STATUS "Getting JSI headers from ${JSI_HEADER_DIR}")
 
 add_library(realm-js-hermes OBJECT
     jsi_init.cpp