Revert "Use amd-llvm as the default toolchain for all RDC builds"

[amd-shiraz]

Reverts #4513

OSError: librdc_bootstrap.so.1: cannot open shared object file: No such file or directory

issue: #4640

[radhaksri]

@bill-shuzhou-liu / @adam360x : Please review and approve as appropriate.

[radhaksri]

Ok, to be followed up by RDC team to address a proper fix..

[ScottTodd]

I'm trying to enable the tests that failed in multi-arch CI with #4647.

Using that, I triggered two test runs that should build and test just the DC Tools Core stage (hopefully faster signal than the non-multi-arch CI on this PR):

• baseline, with the original commit that we suspect broke the tests: https://github.com/ROCm/TheRock/actions/runs/24577210341
• with the revert: https://github.com/ROCm/TheRock/actions/runs/24577245561

(Those were triggered with prebuilt stages foundation,compiler-runtime,math-libs,comm-libs,debug-tools,profiler-apps,iree-compiler,fusilli-libs,media-libs and workflow run id 24564363941 from https://github.com/ROCm/TheRock/actions/runs/24564363941/job/71826804444)

[ScottTodd]

• baseline, with the original commit that we suspect broke the tests: https://github.com/ROCm/TheRock/actions/runs/24577210341

• with the revert: https://github.com/ROCm/TheRock/actions/runs/24577245561

baseline has

Fri, 17 Apr 2026 17:32:31 GMT OSError: librdc_bootstrap.so.1: cannot open shared object file: No such file or directory

revert does not. Both have unrelated errors that I'll need to resolve as part of running these tests on multi-arch CI.

So this revert looks like it does fix the relevant tests.

[marbre]

We have enough signal (and approvals) that to assume this revert fixes the problem observed. Merging without waiting for full CI signal.