Add new build flag for Khmer font update

Bug: 381019613
Test: Manually done
Test: build-flag --all-releases get RELEASE_PACKAGE_NOTO_SANS_KHMER_VERSION
Flag: RELEASE_PACKAGE_NOTO_SANS_KHMER_VERSION
Ignore-AOSP-First: AOSP is not ready for flagging
Change-Id: Ic47d42e8d6b5aabbd16dc3ed2c361b23d62f8e8f
2 files changed