fix: files included twice when they match include_spec (#857)

Currently if a file matches the explicit `sdist.include` it is included
twice in the source distribution.

This causes an error with some package managers such as `uv` (See
abetlen/llama-cpp-python#1670 (comment)).

Author: abetlen

src/scikit_build_core/build/_file_processor.py

@@ -59,6 +59,7 @@ def each_unignored_file(
             # Always include something included
             if include_spec.match_file(p):
                 yield p
+                continue
 
             # Ignore from global ignore
             if exclude_spec.match_file(p):