Re-enable spl downstream build

[KirillLykov]

Problem

Re-enable spl downstream build which was disabled after borsh upgrade.
See #32378

Summary of Changes

[yihau]

Thank you <3

btw, I'm thinking do we want to make this one happen in this same PR. 072884d

I modified it accidentally but the fix hasn't merged cuz some issues. 😢

[yihau]

(btw, this PR is good enough to me! I can fix the error in my original PR if it doesn't happen in this one!)

[KirillLykov]

Thank you <3

btw, I'm thinking do we want to make this one happen in this same PR. 072884d

I modified it accidentally but the fix hasn't merged cuz some issues. 😢

My understanding is that you propose to run test instead of build. I'm not sure about doing cargo-test-sbf because there is timeout 30min currently and I don't know how long test will take.
I think we should not mix re-enabling build and enabling tests because each change might go wrong for some reason and it will be harder to track.

[yihau]

yeah. no problem. I can fix it in another PR.
tbh, we did test before. one of my reorg PR broke it.

solana/scripts/build-downstream-projects.sh

Line 72 in 304c13d

$cargo_test_bpf --manifest-path "$program"/Cargo.toml

(^^^ from the v1.14 branch)

[joncinque]

Looks good to me! It's too bad it doesn't run the job in this PR though