Include RobotoFlex into AOSP system image

Bug: 235303866
Test: Manually done
Change-Id: I8ff5ef9441b8103d87bd4eb575e5abe87a2750c1
diff --git a/target/product/handheld_system.mk b/target/product/handheld_system.mk
index 41233b2..d965367 100644
--- a/target/product/handheld_system.mk
+++ b/target/product/handheld_system.mk
@@ -27,6 +27,7 @@
 $(call inherit-product-if-exists, external/google-fonts/source-sans-pro/fonts.mk)
 $(call inherit-product-if-exists, external/noto-fonts/fonts.mk)
 $(call inherit-product-if-exists, external/roboto-fonts/fonts.mk)
+$(call inherit-product-if-exists, external/roboto-flex-fonts/fonts.mk)
 $(call inherit-product-if-exists, external/hyphenation-patterns/patterns.mk)
 $(call inherit-product-if-exists, frameworks/base/data/keyboards/keyboards.mk)
 $(call inherit-product-if-exists, frameworks/webview/chromium/chromium.mk)