selftests/bpf: use host CPU features in JIT disassembler

selftests/bpf: use host CPU features in JIT disassembler

Pass the host CPU name and feature string to
LLVMCreateDisasmCPUFeatures() instead of using LLVMCreateDisasm(), so
the disassembler correctly decodes CPU-specific instructions and
extensions such as RISC-V compressed and vector instructions.

Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20260602205847.102825-2-varunrmallya@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>