Bots not collecting perf data

[brson]

With the recent build changes it looks like the bots no longer know how to find the perf data:

perf compile: rustc-perf find: `test/perf': No such file or directory Performance counter stats for 'i686-unknown-linux-gnu/stage2/bin/rustc -O --target=i686-unknown-linux-gnu -o rustc-perf /home/rustbuild/src/rustbot/workspace-snap-stage3-x86_64-unknown-linux-gnu/src/src/comp/rustc.rc' (3 runs): 60334.848310 task-clock-msecs # 1.000 CPUs ( +- 0.368% ) 26269 context-switches # 0.000 M/sec ( +- 15.837% ) 239 CPU-migrations # 0.000 M/sec ( +- 23.752% ) 62376 page-faults # 0.001 M/sec ( +- 2.260% ) 200897923984 cycles # 3329.716 M/sec ( +- 0.364% ) 275408777093 instructions # 1.371 IPC ( +- 0.025% ) 58365830745 branches # 967.365 M/sec ( +- 0.026% ) 986313285 branch-misses # 1.690 % ( +- 0.236% ) 1072457417 cache-references # 17.775 M/sec ( +- 0.385% ) 58152792 cache-misses # 0.964 M/sec ( +- 0.159% ) 60.357982442 seconds time elapsed ( +- 0.308% )```

[nikomatsakis]

I believe this ought to be fixed as of @c1be673e

[nikomatsakis]

Fixed.