ios: use file to override native modules build

Reads the contents of a react-native project's file for overriding
the automatic native modules detection.

scripts/module-postlink.js

@@ -148,6 +148,15 @@ if ( detectedConfigs && detectedConfigs.ios && detectedConfigs.ios.pbxprojPath)
     var rebuildNativeModulesBuildPhaseScript = `
 set -e
 if [ -z "$NODEJS_MOBILE_BUILD_NATIVE_MODULES" ]; then
+# If build native modules preference is not set, look for it in the project's
+#nodejs-assets/BUILD_NATIVE_MODULES.txt file.
+NODEJS_ASSETS_DIR="$( cd "$PROJECT_DIR" && cd ../nodejs-assets/ && pwd )"
+PREFERENCE_FILE_PATH="$NODEJS_ASSETS_DIR/BUILD_NATIVE_MODULES.txt"
+if [ -f "$PREFERENCE_FILE_PATH" ]; then
+  NODEJS_MOBILE_BUILD_NATIVE_MODULES="$(cat $PREFERENCE_FILE_PATH | xargs)"
+fi
+fi
+if [ -z "$NODEJS_MOBILE_BUILD_NATIVE_MODULES" ]; then
 # If build native modules preference is not set, try to find .gyp files
 #to turn it on.
 gypfiles=($(find "$CODESIGNING_FOLDER_PATH/nodejs-project/" -type f -name "*.gyp"))
@@ -192,6 +201,15 @@ popd
     var signNativeModulesBuildPhaseScript = `
 set -e
 if [ -z "$NODEJS_MOBILE_BUILD_NATIVE_MODULES" ]; then
+# If build native modules preference is not set, look for it in the project's
+#nodejs-assets/BUILD_NATIVE_MODULES.txt file.
+NODEJS_ASSETS_DIR="$( cd "$PROJECT_DIR" && cd ../nodejs-assets/ && pwd )"
+PREFERENCE_FILE_PATH="$NODEJS_ASSETS_DIR/BUILD_NATIVE_MODULES.txt"
+if [ -f "$PREFERENCE_FILE_PATH" ]; then
+  NODEJS_MOBILE_BUILD_NATIVE_MODULES="$(cat $PREFERENCE_FILE_PATH | xargs)"
+fi
+fi
+if [ -z "$NODEJS_MOBILE_BUILD_NATIVE_MODULES" ]; then
 # If build native modules preference is not set, try to find .gyp files
 #to turn it on.
 gypfiles=($(find "$CODESIGNING_FOLDER_PATH/nodejs-project/" -type f -name "*.gyp"))