[RFC] Prefix test invocations with the given tool for llvm-lit

Hi, I am developing new ISA in LLVM and usually a real machine is not available to me. So I heavily depends on simulators to check the functionality.

LLVM test suite is good checker and I’d like to run the suite on the simulators to check the correctness of the compiler for new ISA.

After following the guide at test-suite Guide — LLVM 17.0.0git documentation and some trial, I proposed a solution here ⚙ D150431 [lit] Add knob --run-prefix to allow developers to run LIT on a simulator when real machine is not available to make it work. The issue I encountered was described at the link too.

I think this method should be helpful for different target ISA tests. And maybe you have a better idea/solution.

Any comments are welcome!