[llvm-exegesis] Use const reference for range variable

In the SubprocessMemory destructor, I was using a normal std::string to
hold the name of the current shared memory name, but a const reference
works just as well in this situation while having better performance
characteristics.

Fixes #90289

GitOrigin-RevId: ad2816e7340be71c93e60b9bb58e107fe1b76e4d
1 file changed