Fix runtime_deps_file arg for tast targets.

TBR=jbudorick

Bug: 876587
Change-Id: Ic121bccd2343fe48eefbbaf2ccf60d2d01969ca2
Reviewed-on: https://chromium-review.googlesource.com/1252911Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595255}

build/config/chromeos/rules.gni

@@ -159,7 +159,7 @@ template("tast_test") {
     testonly = true
     tast_tests = invoker.tast_tests
     generated_script = "$root_build_dir/bin/run_${target_name}"
-    runtime_deps_file = "$root_out_dir/${target_name}/.runtime_deps"
+    runtime_deps_file = "$root_out_dir/${target_name}.runtime_deps"
     deploy_chrome = true
     data_deps = [
       "//:chromiumos_preflight",  # Builds the browser.