Recipes: make cwd default to slave_build

scripts/slave/recipes/bisect_test/example_bisect_results.expected/failed_test.json

 [
   {
     "cmd": [
       "echo",
       "{\n  \"bad_revision\": \"314017\", \n  \"bug_id\": \"\", \n  \"builder_host\": \"master4.golo.chromium.org\", \n  \"builder_port\": \"8341\", \n  \"command\": \"src/tools/perf/run_benchmark -v --browser=release smoothness.tough_scrolling_cases\", \n  \"dummy_builds\": \"True\", \n  \"good_revision\": \"314015\", \n  \"gs_bucket\": \"chrome-perf\", \n  \"max_time_minutes\": \"5\", \n  \"metric\": \"mean_input_event_latency/mean_input_event_latency\", \n  \"repeat_count\": \"2\", \n  \"skip_gclient_ops\": \"True\", \n  \"test_type\": \"perf\", \n  \"truncate_percent\": \"0\"\n}"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "config"
   },
   {
     "cmd": [
       "git",
       "log",
       "--format=hash:%H",
       "--grep",
       "Cr-Commit-Position: refs/heads/master@{#314017}",
       "-1",
@@ skipping 36 matching lines @@
       "c001c0de"
     ],
     "cwd": "[TMP_BASE]/bogus_tmp_1",
     "name": "resolving hash c001c0de",
     "stdout": "/path/to/tmp/"
   },
   {
     "cmd": [
       "cat"
     ],
+    "cwd": "[SLAVE_BUILD]",
     "name": "Results",
     "stdin": "\n===== BISECT JOB RESULTS =====\nStatus: Failed\n\nTest Command: src/tools/perf/run_benchmark -v --browser=release smoothness.tough_scrolling_cases\nTest Metric: mean_input_event_latency/mean_input_event_latency\nRelative Change: None\nEstimated Confidence: 0.99%\nRetested CL with revert: Not Implemented.\n\n\n===== WARNINGS =====\nThe following warnings were raised by the bisect job:\n\n * This is a demo warning\n\n\n===== TESTED REVISIONS =====\ncommit_pos revision_string mean_value std_err good_or_bad? tested? culprit? \n\n\n\n==== INSTRUCTIONS TO REPRODUCE ====\nTo run locally:\n - Use the test command given under 'BISECT JOB RESULTS' above.\n - Consider using a profiler. Pass --profiler=list to list available profilers.\n\n\nTo reproduce on a performance try bot:\nsrc/tools/perf/run_benchmark -v --browser=<bot-name> smoothness.tough_scrolling_cases\n(Where <bot-name> comes from tools/perf/run_benchmark --browser=list)\n\nFor more details please visit\nhttps://sites.google.com/a/chromium.org/dev/developers/performance-try-bots\n\n\n| O O | Visit http://www.chromium.org/developers/core-principles for Chrome's\n|  X  | policy on perf regressions. Contact chrome-perf-dashboard-team with any\n| / \\ | questions or suggestions about bisecting. THANK YOU."
   }
 ]