[libc++] Make sure we use POSIX paths in header_information.py

[ldionne]

Summary

Otherwise, the various lists of headers have different content based
on whether they are run on Windows or other platforms, which makes it
really difficult to write .gen.py tests correctly.

[Mordante]

LGTM!

libcxx/utils/libcxx/test/header_information.py

133–136

I really dislike this nested os.path.dirname, but it is pre-existing.

[Mordante]

Now with approval selected ;-)

libcxx/utils/libcxx/test/header_information.py

def is_header(file):
     """Returns whether the given file is a header (i.e. not a directory or the modulemap file)."""
     return (
         not file.is_dir()
         and not file.name == "module.modulemap.in"
         and not file.name == "CMakeLists.txt"
         and file.name != "libcxx.imp"
     )
 
-monorepo_root = pathlib.Path(
-    os.path.dirname(os.path.dirname(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))))
-)
-include = pathlib.Path(os.path.join(monorepo_root, "libcxx", "include"))
-test = pathlib.Path(os.path.join(monorepo_root, "libcxx", "test"))
-assert monorepo_root.exists()
+libcxx_root = pathlib.Path(os.path.dirname(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))))
+include = pathlib.Path(os.path.join(libcxx_root, "include"))
+test = pathlib.Path(os.path.join(libcxx_root, "test"))
+assert libcxx_root.exists()
 
 toplevel_headers = sorted(
-    str(p.relative_to(include)) for p in include.glob("[a-z]*") if is_header(p)
+    p.relative_to(include).as_posix() for p in include.glob("[a-z]*") if is_header(p)
 )
 experimental_headers = sorted(
-    str(p.relative_to(include))
-    for p in include.glob("experimental/[a-z]*")
-    if is_header(p)
+    p.relative_to(include).as_posix() for p in include.glob("experimental/[a-z]*") if is_header(p)
 )
 public_headers = toplevel_headers + experimental_headers
 private_headers = sorted(
-    str(p.relative_to(include))
-    for p in include.rglob("*")
-    if is_header(p)
+    p.relative_to(include).as_posix() for p in include.rglob("*") if is_header(p)
                                                                      and str(p.relative_to(include)).startswith("__")
                                                                      and not p.name.startswith("pstl")
 )
 variables = {
     "toplevel_headers": toplevel_headers,
     "experimental_headers": experimental_headers,
     "public_headers": public_headers,
     "private_headers": private_headers,
     "header_restrictions": header_restrictions,
     "private_headers_still_public_in_modules": private_headers_still_public_in_modules,
 }