[llvm] [llvm][support] Refactor symlink handling and add readlink (PR #184256)

[Michael Spencer via llvm-commits]

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@@ -338,8 +338,52 @@ std::error_code create_directory(const Twine &path, bool IgnoreExisting,
   return std::error_code();
 }
 
-// We can't use symbolic links for windows.
+std::error_code create_symlink(const Twine &to, const Twine &from) {
+  SmallVector<wchar_t, 128> wide_from;
+  SmallVector<wchar_t, 128> wide_to;
+  if (std::error_code ec = widenPath(from, wide_from))
+    return ec;
+  if (std::error_code ec = widenPath(to, wide_to))
+    return ec;
+
+  // The Win32 API normally allows forward slashes, but under some cases it does
+  // not correctly handle them in the target of a symlink.
+  for (wchar_t &C : wide_to)
+    if (C == L'/')
+      C = L'\\';
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Bigcheese wrote:

This needs to work on the wide version of the path.

https://github.com/llvm/llvm-project/pull/184256