fix: use cross-platform toStdString in FlameHasher

Almost the same issue from toml++ :p

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/modplatform/helpers/HashUtils.cpp

@@ -4,6 +4,7 @@
 #include <QFile>
 
 #include "FileSystem.h"
+#include "StringUtils.h"
 
 #include <MurmurHash2.h>
 
@@ -66,7 +67,7 @@ void FlameHasher::executeTask()
     // CF-specific
     auto should_filter_out = [](char c) { return (c == 9 || c == 10 || c == 13 || c == 32); };
 
-    std::ifstream file_stream(m_path.toStdString(), std::ifstream::binary);
+    std::ifstream file_stream(StringUtils::toStdString(m_path), std::ifstream::binary);
     // TODO: This is very heavy work, but apparently QtConcurrent can't use move semantics, so we can't boop this to another thread.
     // How do we make this non-blocking then?
     m_hash = QString::number(MurmurHash2(std::move(file_stream), 4 * MiB, should_filter_out));