Running tools/perf/run_benchmark, I often hit the case that

a) I don't have the required binary/apk built, or
b) I do have it, but it's stale

Since the benchmark runner already knows my output directory and binary, it could probably figure out if there's a matching output directory without the binary (in which case it could print "please build <target>" as an error), and it could figure out if its binary is stale (e.g. check if "ninja -n <binary>" does anything, and print a warning if yes).

Even better, there could be a --build flag which triggers the build (probably not on by default). That would save me a few helper scripts.