Merge pull request cupy#8927 from kmaehashi/fix-cache-key-calc

Use relative path of header files to generate cache key

install/cupy_builder/_context.py

@@ -66,7 +66,8 @@ def __init__(
         hasher = hashlib.sha1(usedforsecurity=False)
         for include_file in include_files:
             with open(include_file, 'rb') as f:
-                hasher.update(include_file.encode())
+                relpath = os.path.relpath(include_file, source_root)
+                hasher.update(relpath.encode())
                 hasher.update(f.read())
                 hasher.update(b'\x00')
         cache_key = hasher.hexdigest()