imagemagick: undisrecommend ghostscript

Closes #32412.
Update xctool to v0.2 for Xcode 6 support

Closes #32417.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
xctool: update 0.2 bottle.
Pass command and arg list into ErrorDuringExecution constructor
Make install name debug output more readable
Remove obsolete nil guard

This was added in 3a7a3619f7016c75c3e53e944221bf7f6354a63b to make the
tests pass, but this method is now stubbed out in the tests, so we can
assume $? will be non-nil.