make vr_assets_profile dir always

This is necessary to make second build no-op.
Without this, following command runs the script always.
$ ninja -C out/android_arm64_dbg_recipe/ gen/tools/perf/contrib/vr_benchmarks/vr_assets_profile

Bug: 914264
Change-Id: I35ff097c6a34318813957b71c690386fc1a7a1e3
Reviewed-on: https://chromium-review.googlesource.com/c/1373734Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615991}

tools/perf/contrib/vr_benchmarks/generate_vr_assets_profile.py

@@ -41,6 +41,8 @@ def main():
   profile_dir = os.path.join(args.output, 'vr_assets_profile')
   if os.path.isdir(profile_dir):
     shutil.rmtree(profile_dir)
+  os.makedirs(profile_dir)
+
   # Check whether there are actually files to copy - if not, the lack of a
   # directory will cause Telemetry to fail if we actually try to use the profile
   # directory. This is a workaround for not being able to check whether we