util: use stronger-guarantee rename method

Use std::filesystem::rename() instead of std::rename(). We rely on the
destination to be overwritten if it exists, but std::rename()'s behavior
is implementation-defined in this case.

src/util/system.cpp

@@ -74,6 +74,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <system_error>
 #include <thread>
 #include <typeinfo>
 
@@ -1061,13 +1062,9 @@ void ArgsManager::LogArgs() const
 
 bool RenameOver(fs::path src, fs::path dest)
 {
-#ifdef WIN32
-    return MoveFileExW(src.wstring().c_str(), dest.wstring().c_str(),
-                       MOVEFILE_REPLACE_EXISTING) != 0;
-#else
-    int rc = std::rename(src.c_str(), dest.c_str());
-    return (rc == 0);
-#endif /* WIN32 */
+    std::error_code error;
+    fs::rename(src, dest, error);
+    return !error;
 }
 
 /**

src/util/system.h

@@ -69,7 +69,13 @@ void DirectoryCommit(const fs::path &dirname);
 bool TruncateFile(FILE *file, unsigned int length);
 int RaiseFileDescriptorLimit(int nMinFD);
 void AllocateFileRange(FILE *file, unsigned int offset, unsigned int length);
+
+/**
+ * Rename src to dest.
+ * @return true if the rename was successful.
+ */
 [[nodiscard]] bool RenameOver(fs::path src, fs::path dest);
+
 bool LockDirectory(const fs::path& directory, const std::string lockfile_name, bool probe_only=false);
 void UnlockDirectory(const fs::path& directory, const std::string& lockfile_name);
 bool DirIsWritable(const fs::path& directory);