Fix some bugs with spaces in directory name.

Any time you use the directory name (`FWDIR`) it needs to be surrounded
in quotes. If you're also using wildcards, you can safely put the quotes
around just `$FWDIR`.

Author: Sarah Gerweck <sarah.a180@gmail.com>

Closes #1756 from sarahgerweck/folderSpaces and squashes the following commits:

732629d [Sarah Gerweck] Fix some bugs with spaces in directory name.
(cherry picked from commit 5507dd8e18fbb52d5e0c64a767103b2418cb09c6)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>