libstdc++: Remove redundant -std=gnu++17 options from filesystem tests

libstdc++: Remove redundant -std=gnu++17 options from filesystem tests

GCC defaults to -std=gnu++17 now anyway, and using it explicitly in the
dg-options directive prevents running these tests with different modes
such as -std=c++17 or -std=gnu++20.

libstdc++-v3/ChangeLog:

	* testsuite/27_io/basic_filebuf/open/char/path.cc: Remove
	-std=gnu++17 from dg-options directive.
	* testsuite/27_io/basic_fstream/cons/char/path.cc: Likewise.
	* testsuite/27_io/basic_fstream/open/char/path.cc: Likewise.
	* testsuite/27_io/basic_ifstream/cons/char/path.cc: Likewise.
	* testsuite/27_io/basic_ifstream/open/char/path.cc: Likewise.
	* testsuite/27_io/basic_ofstream/cons/char/path.cc: Likewise.
	* testsuite/27_io/basic_ofstream/open/char/path.cc: Likewise.
	* testsuite/27_io/filesystem/directory_entry/86597.cc: Likewise.
	* testsuite/27_io/filesystem/directory_entry/lwg3171.cc:
	Likewise.
	* testsuite/27_io/filesystem/file_status/1.cc: Likewise.
	* testsuite/27_io/filesystem/filesystem_error/cons.cc: Likewise.
	* testsuite/27_io/filesystem/filesystem_error/copy.cc: Likewise.
	* testsuite/27_io/filesystem/iterators/91067.cc: Likewise.
	* testsuite/27_io/filesystem/iterators/caching.cc: Likewise.
	* testsuite/27_io/filesystem/iterators/directory_iterator.cc:
	Likewise.
	* testsuite/27_io/filesystem/iterators/pop.cc: Likewise.
	* testsuite/27_io/filesystem/iterators/recursion_pending.cc:
	Likewise.
	* testsuite/27_io/filesystem/iterators/recursive_directory_iterator.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/absolute.cc: Likewise.
	* testsuite/27_io/filesystem/operations/all.cc: Likewise.
	* testsuite/27_io/filesystem/operations/canonical.cc: Likewise.
	* testsuite/27_io/filesystem/operations/copy.cc: Likewise.
	* testsuite/27_io/filesystem/operations/copy_file.cc: Likewise.
	* testsuite/27_io/filesystem/operations/create_directories.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/create_directory.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/create_symlink.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/current_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/equivalent.cc: Likewise.
	* testsuite/27_io/filesystem/operations/exists.cc: Likewise.
	* testsuite/27_io/filesystem/operations/file_size.cc: Likewise.
	* testsuite/27_io/filesystem/operations/is_empty.cc: Likewise.
	* testsuite/27_io/filesystem/operations/last_write_time.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/permissions.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/proximate.cc: Likewise.
	* testsuite/27_io/filesystem/operations/read_symlink.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/relative.cc: Likewise.
	* testsuite/27_io/filesystem/operations/remove.cc: Likewise.
	* testsuite/27_io/filesystem/operations/remove_all.cc: Likewise.
	* testsuite/27_io/filesystem/operations/rename.cc: Likewise.
	* testsuite/27_io/filesystem/operations/resize_file.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/space.cc: Likewise.
	* testsuite/27_io/filesystem/operations/status.cc: Likewise.
	* testsuite/27_io/filesystem/operations/symlink_status.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/temp_directory_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/operations/weakly_canonical.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/append/path.cc: Likewise.
	* testsuite/27_io/filesystem/path/append/source.cc: Likewise.
	* testsuite/27_io/filesystem/path/assign/assign.cc: Likewise.
	* testsuite/27_io/filesystem/path/assign/copy.cc: Likewise.
	* testsuite/27_io/filesystem/path/compare/compare.cc: Likewise.
	* testsuite/27_io/filesystem/path/compare/lwg2936.cc: Likewise.
	* testsuite/27_io/filesystem/path/compare/path.cc: Likewise.
	* testsuite/27_io/filesystem/path/compare/strings.cc: Likewise.
	* testsuite/27_io/filesystem/path/concat/92853.cc: Likewise.
	* testsuite/27_io/filesystem/path/concat/94063.cc: Likewise.
	* testsuite/27_io/filesystem/path/concat/path.cc: Likewise.
	* testsuite/27_io/filesystem/path/concat/strings.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/80762.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/90281.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/90634.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/copy.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/default.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/construct/format.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/locale.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/range.cc: Likewise.
	* testsuite/27_io/filesystem/path/construct/string_view.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/extension.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/filename.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/parent_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/relative_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/root_directory.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/root_name.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/root_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/decompose/stem.cc: Likewise.
	* testsuite/27_io/filesystem/path/factory/u8path-char8_t.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/factory/u8path.cc: Likewise.
	* testsuite/27_io/filesystem/path/generation/normal.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/generation/normal2.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/generation/proximate.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/generation/relative.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/generic/94242.cc: Likewise.
	* testsuite/27_io/filesystem/path/generic/generic_string.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/generic/utf.cc: Likewise.
	* testsuite/27_io/filesystem/path/generic/wchar_t.cc: Likewise.
	* testsuite/27_io/filesystem/path/io/dr2989.cc: Likewise.
	* testsuite/27_io/filesystem/path/itr/components.cc: Likewise.
	* testsuite/27_io/filesystem/path/itr/traversal.cc: Likewise.
	* testsuite/27_io/filesystem/path/modifiers/clear.cc: Likewise.
	* testsuite/27_io/filesystem/path/modifiers/make_preferred.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/modifiers/remove_filename.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/modifiers/replace_extension.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/modifiers/replace_filename.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/modifiers/swap.cc: Likewise.
	* testsuite/27_io/filesystem/path/native/alloc.cc: Likewise.
	* testsuite/27_io/filesystem/path/native/string-char8_t.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/native/string.cc: Likewise.
	* testsuite/27_io/filesystem/path/nonmember/append.cc: Likewise.
	* testsuite/27_io/filesystem/path/nonmember/cmp.cc: Likewise.
	* testsuite/27_io/filesystem/path/nonmember/hash_value.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/empty.cc: Likewise.
	* testsuite/27_io/filesystem/path/query/empty_neg.cc:
	* testsuite/27_io/filesystem/path/query/has_extension.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_filename.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_parent_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_relative_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_root_directory.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_root_name.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_root_path.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/has_stem.cc: Likewise.
	* testsuite/27_io/filesystem/path/query/is_absolute.cc:
	Likewise.
	* testsuite/27_io/filesystem/path/query/is_relative.cc:
	Likewise.
	* testsuite/experimental/filesystem/path/construct/string_view.cc:
	Likewise.