file(REMOVE) should not cause an error if given an empty list of files
Consider code like the following:
file(GLOB fileList "some/path/blah*.txt")
file(REMOVE ${fileList})
If the file glob returns an empty list, the file(REMOVE)
command fails with an error stating that the file command requires at least two arguments. However, the docs for file(REMOVE)
show that the file list is actually optional. I interpret that to mean the file list can be zero or more items, not one or more items. I think we should support this specific scenario.