Disable extensions not running with 1.9.x anymore

[herndlm]

similar as 3e10ce4

the idea is to make 1.9.x PRs green again, e.g. phpstan/phpstan-src#2146

an alternative to this approach might be to lock extensions to an old commit maybe that is still compatible with 1.9.x? in the matrix this could be something like phpstan-strict-rules:<commit-hash> or so..

[ondrejmirtes]

 lock extensions to an old commit

Yes, that's what I'd like to do this time :) Thanks. We need to introduce a new env variable/argument going into test-extensions.sh.

[herndlm]

Yes, that's what I'd like to do this time :) Thanks. We need to introduce a new env variable/argument going into test-extensions.sh.

I'm already working on it, I'm bad with github actions though, which I'm currently completely ignoring. What do you think of my initially mentioned format? I can do the rest in test-extensions.sh then. Or is there a better way to configure this in the matrix?