Unable to build on linux, problems with `-fblocks` and libblocksruntime

Hi!

I'm having a hard time compiling swift on linux. I have fired up the ubuntu container, checked out the 5.5.1 release, called update-checkout, and then called build-script --release-debuginfo --test.

After quite some time, while compiling part of LLVM, I get an error urging me to use the -fblocks option. I managed to slightly advance playing around with env variables (CXX, CXXFLAGS and the rest of the lot), as well as having to pass --extra-cmake-options to set up those flags, and then also installing libblocksruntime-dev (maybe it should be added to the container?). I still get quite some problems with this blocks dependency.

I can produce some gist output of the build if it helps, but maybe you can already point me in the right direction based on what I wrote? I even went and read the logs of a jenkins build, but I did not find anything that could explain why it does not work on my setup.

By the way, I'm mainly interested in compiling the frontend tool lib, so maybe I don't need to build everything?

That is the compiler frontend, so I think it will require LLVM. Are you sure you checked out the right LLVM tag? Run git status in the llvm-project checkout and make sure it says HEAD detached at swift-5.5.1-RELEASE. If not that, we'll need some compiler error output.

hmm, turns out, this was probably due either to leftovers from an earlier trial on my native ubuntu 21.10 system before moving to the containerized 20.04 system, or to an interrupted run of update-checkout... Starting again from a clean slate ran just fine.