util/glsl2spirv: fixup the generated depfile when copying sources

So that the depfile contains a reference to the original source rather
than the copied one. This is necessary to avoid ninja not finding the
copy and causing spurious rebuilds when the copy has been removed, as
well as correctly tracking changes to the input files.

fixes: 46644ba371

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30132>

src/util/glsl2spirv.py

@@ -145,7 +145,7 @@ def postprocess_file(args: 'Arguments') -> None:
         w.writelines(lines)
 
 
-def preprocess_file(args: 'Arguments', origin_file: T.TextIO, directory: os.PathLike) -> str:
+def preprocess_file(args: 'Arguments', origin_file: T.TextIO, directory: os.PathLike, filemap: T.Dict[str, str]) -> str:
     with open(os.path.join(directory, os.path.basename(origin_file.name)), "w") as copy_file:
         lines = origin_file.readlines()
 
@@ -157,13 +157,36 @@ def preprocess_file(args: 'Arguments', origin_file: T.TextIO, directory: os.Path
 
         copy_file.writelines(lines)
 
+    filemap[copy_file.name] = origin_file.name
     return copy_file.name
 
 
+def fixup_depfile(depfile: str, filemap: T.Mapping[str, str]) -> None:
+    """Replace generated file references in the depfile with their source.
+    """
+    depends: T.List[str] = []
+    out: T.Optional[str] = None
+    with open(depfile, 'r') as f:
+        for line in f.readlines():
+            if ':' in line:
+                out, line = line.split(':', 1)
+            depends.extend(l.strip() for l in line.split())
+
+    with open(depfile, 'w') as f:
+        f.write(out)
+        f.write(': ')
+        for dep in depends:
+            f.write(filemap.get(dep, dep))
+            f.write(' ')
+        f.write('\n')
+
+
 def process_file(args: 'Arguments') -> None:
+    filemap: T.Dict[str, str] = {}
+
     with open(args.input, "r") as infile:
-        copy_file = preprocess_file(args, infile,
-                                    os.path.dirname(args.output))
+        copy_file = preprocess_file(
+            args, infile, os.path.dirname(args.output), filemap)
 
     cmd_list = [args.glslang]
 
@@ -184,7 +207,6 @@ def process_file(args: 'Arguments') -> None:
 
     for f in args.includes:
         cmd_list.append('-I' + f)
-
     for d in args.defines:
         cmd_list.append('-D' + d)
 
@@ -207,6 +229,9 @@ def process_file(args: 'Arguments') -> None:
     if args.create_entry is not None:
         os.remove(copy_file)
 
+    if args.depfile is not None:
+        fixup_depfile(args.depfile, filemap)
+
 
 def main() -> None:
     args = get_args()