[vcpkg] Make Filesystem::remove_all faster #7570

I added benchmarks to measure how fast the parallel remove_all code was
-- it turns out, about 3x slower than stdfs::remove_all. Since this was
the case, I removed all of the parallelism and rewrote it serially, and
ended up about 30% faster than stdfs::remove_all (in addition to
supporting symlinks).

In addition, I did the following three orthogonal changes:
  - simplified the work queue, basing it on Billy O'Neal's idea
  - Fix warnings on older versions of compilers in tests, by splitting
    the pragmas out of pch.h.
  - Ran clang-format on some files

In fixing up remove_all, the following changes were made:
  - On Windows, regular symlinks and directory symlinks are distinct;
    as an example, to remove directory symlinks (and junctions, for that
    matter), one must use RemoveDirectory. Only on Windows, I added new
    `file_type` and `file_status` types, with `file_type` including a new
    `directory_symlink` enumerator, and `file_status` being exactly the
    same as the old one except using the new `file_type`. On Unix, I
    didn't make that change since they don't make a distinction.
  - I added new `symlink_status` and `status` functions which use the
    new `file_status` on Windows.
  - I made `Filesystem::exists` call `fs::exists(status(p))`, as opposed
    to the old version which called `stdfs::exists` directly.
  - Added benchmarks to `vcpkg-test/files.cpp`. They test the
    performance of `remove_all` on small directories (~20 files), with
    symlinks and without, and on large directories (~2000 files), with
    symlinks and without.

1 files changed, 2 insertions, 10 deletions

diff --git a/toolsrc/include/pch.h b/toolsrc/include/pch.h
index 15ec25e76..ce2a7c9c5 100644
--- a/toolsrc/include/pch.h
+++ b/toolsrc/include/pch.h
@@ -1,14 +1,6 @@
 #pragma once
 
-#if defined(_MSC_VER) && _MSC_VER < 1911
-// [[nodiscard]] is not recognized before VS 2017 version 15.3
-#pragma warning(disable : 5030)
-#endif
-
-#if defined(__GNUC__) && __GNUC__ < 7
-// [[nodiscard]] is not recognized before GCC version 7
-#pragma GCC diagnostic ignored "-Wattributes"
-#endif
+#include <vcpkg/pragmas.h>
 
 #if defined(_WIN32)
 #define NOMINMAX
@@ -38,8 +30,8 @@
 #include <cstddef>
 #include <cstdint>
 #define _SILENCE_EXPERIMENTAL_FILESYSTEM_DEPRECATION_WARNING
-#include <experimental/filesystem>
 #include <cstring>
+#include <experimental/filesystem>
 #include <fstream>
 #include <functional>
 #include <iomanip>