Reland check-builtins target for LLVM_ENABLE_RUNTIMES (#171941)

Reland https://github.com/llvm/llvm-project/pull/166837 and
https://github.com/llvm/llvm-project/pull/171741

(Reverts the revert in #171940)

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Co-authored-by: Petr Hosek <phosek@google.com>
GitOrigin-RevId: d1aca4b1471353a126db0954c8f998fca7ba3752
5 files changed