Patch to enable compilation with JDK 21
Ideally, we need to upgrade the packaging repository to a versioned one, where branches for 11, 17, 21, master point to openjdk/jfx11u, openjdk/jfx17u, openjdk/jfx21u and openjdk/jfx. In the interim, here is a patch to ensure the current package builds with openjdk-21 as default-jdk.
Build tested here: https://launchpad.net/~pushkarnk/+archive/ubuntu/migrate21/+build/27777166