tools: art script fix for spuriously creating "{arm,arm64,mips,mips64,x86,x86_64}" directory

Also removes hardcoding of the architectures list.

Manually tested with/without --profile, on host/target, and with non-rooted adb.

Test: art -cp benchmarks.dex BenchmarkMain
Change-Id: I4cec02bb80c905bfce174135e8c2a6b6dd6ac42d