[SYCL][Graph] Fix E2E disabled RUN lines

[EwanC]

We were using the x prefix to the RUN lit command to comment out a RUN check. However, LIT still detects this as a RUN command, which illustrated in a CI fail of this test recently https://github.com/intel/llvm/actions/runs/10198164930/job/28215254220

Fixed by changing xRUN to RUNx which I've verified locally is not detected as a RUN command by LIT, and can be used to comment the RUN command out.

Relates to #14473

[ayylol]

If you'd like to keep the line commented rather than deleting it you could replace the xRUN with RUNx, that seems to not be picked up by lit correctly.
For example like this test: https://github.com/intel/llvm/blob/sycl/sycl/test-e2e/Basic/fpga_tests/fpga_io_pipes.cpp#L3

[EwanC]

If you'd like to keep the line commented rather than deleting it you could replace the xRUN with RUNx, that seems to not be picked up by lit correctly. For example like this test: https://github.com/intel/llvm/blob/sycl/sycl/test-e2e/Basic/fpga_tests/fpga_io_pipes.cpp#L3

Great tip thanks, verified that locally and updated the PR to that

[EwanC]

@intel/llvm-gatekeepers The CI fail is from the problematic HIP runner. This PR disables a E2E RUN line that is guarded by %if level_zero, so should be okay to merge.