Enable const-vector.rs test on RISC-V (riscv64)
This PR replaces [#144283](https://github.com/rust-lang/rust/pull/144283) to resolve merge conflicts.
This PR adds support for running the `tests/codegen/const-vector.rs` test on the RISC-V (riscv64) architecture.
Previously, this test would fail on RISC-V targets due to architecture-specific code generation issues. This patch modifies the test to ensure compatibility while preserving its intent.
The change has been tested locally using `./x test` on a riscv64 target, and the test now passes as expected.
### Notes:
- This change is scoped specifically to improve RISC-V compatibility.
- It does not affect behavior or test results on other architectures.
a262dadc40