gen_descriptor: compress() forward-slash source globs on windows

compress() keyed dirs by str(p.parent) -> backslashes on windows Path -> mixed
'3rdparty\libjpeg-turbo\simd/jsimd.c' source globs (invalid lua escape, wrong
glob separators). Use p.parent.as_posix(). Descriptor otherwise generated fully
(2845 lines, mcpp parse OK: windows sources 45/inc 22/gen 174).

Author: Sunrisepeak

tools/compat-opencv/gen_descriptor.py

@@ -292,10 +292,10 @@ def compress(entries):
     for e in entries:
         if e.startswith("*/"):
             p = Path(e[2:])
-            by_dir[("*", str(p.parent), p.suffix)].append(p.name)
+            by_dir[("*", p.parent.as_posix(), p.suffix)].append(p.name)  # as_posix: forward slashes on windows
         else:  # mcpp_generated/...
             p = Path(e)
-            by_dir[("g", str(p.parent), p.suffix)].append(p.name)
+            by_dir[("g", p.parent.as_posix(), p.suffix)].append(p.name)
     out = []
     for (kind, d, suf), names in sorted(by_dir.items()):
         if kind == "*":