I hope this is the right StackExchange forum to post this to, but how would one update a project, which depends on two other projects, which they themselves got upgraded and are not backwards compatible?

My situation, I am working on the sourcecode of PostgreSQL and have implemented a project in five years ago. This project relies on LLVM and its LLVM-C-API. PostgreSQL and LLVM have change quite a bit in the last five years and introduced new versions that are no longer supporting and even breaking with some pieces of my old code.

Now to my question, is there a fancy and “right, correct” way to upgrade PostgreSQL and LLVM to their newest versions and then integrate my project again.
My solution right now would be to build the project, and solwly add all changed pieces one by one, and if something breaks, I’ll try to fix that according to the newest docs of either LLVM or PSQL.
Or is there a better way?