[fuchsia] use /tmp instead of /data for package install

Previously the runner script was copying packages to /data when
installing them. On some devices (e.g. VIM2) /data is significantly slower
than /tmp. On VIM2 This change reduces media_unittests installation delay
from more than 45s to less than 5s.

Change-Id: Iea4a25abede1f41b28c7194969eb62286f476bbc
Reviewed-on: https://chromium-review.googlesource.com/c/1284392Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600674}

build/fuchsia/run_package.py

@@ -105,7 +105,7 @@ def RunPackage(output_dir, target, package_path, package_name, package_deps,
       logging.info('Installing ' + os.path.basename(next_package_path) + '.')
 
       # Copy the package archive.
-      install_path = os.path.join('/data', os.path.basename(next_package_path))
+      install_path = os.path.join('/tmp', os.path.basename(next_package_path))
       target.PutFile(next_package_path, install_path)
 
       # Install the package.