icecc-create-env: Allow multiple tool aliases

When files are added to the environment, multiple aliases can be given
for the file (by calling add_path multiple times with a second
argument). All of these names will end up with a symlink to the original
file.

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>