One line fix to work around minfs

This CL adds a quick change to boot_data.py that makes the output
directory path absolute before provisioning SSH files, to work around
ZX-2397

Bug: https://fuchsia.atlassian.net/browse/ZX-2397
Change-Id: Iae0c2f8bd992e14bc3d7bcce88c82e65407b829b
Reviewed-on: https://chromium-review.googlesource.com/1147247
Commit-Queue: Stephan Stross <stephanstross@google.com>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577317}

build/fuchsia/boot_data.py

@@ -114,6 +114,9 @@ def ConfigureDataFVM(output_dir, output_type):
                sparse/compressed FVM file."""
 
   logging.debug('Building /data partition FVM file.')
+  # minfs expects absolute paths(bug:
+  #   https://fuchsia.atlassian.net/browse/ZX-2397)
+  output_dir = os.path.abspath(output_dir)
   with tempfile.NamedTemporaryFile() as data_file:
     # Build up the minfs partition data and install keys into it.
     ssh_config, ssh_data = _ProvisionSSH(output_dir)