Fix codecvt errors on OS X

When launching Aegisub from Finder (but not via open), using the UTF-8
version of the locale breaks things for whatever reason, but fortunately
it's unneccesary as paths on OS X are always UTF-8 even if the locale
isn't.

Closes #1685.

aegisub/src/main.cpp

@@ -118,7 +118,15 @@ bool AegisubApp::OnInit() {
 
 	// Set the global locale to the utf-8 version of the current locale
 	std::locale::global(boost::locale::generator().generate(""));
+
+#ifndef __APPLE__
+	// Boost.FileSystem always uses UTF-8 for paths on OS X (since paths
+	// actually are required to be UTF-8 strings rather than just opaque binary
+	// blobs like on Linux), so there's no need to imbue the new locale and in
+	// fact it actively breaks things for unknown reasons when launching the
+	// app from Finder (but not from the command line).
 	boost::filesystem::path::imbue(std::locale());
+#endif
 
 	// Pointless `this` capture required due to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494
 	agi::dispatch::Init([this](agi::dispatch::Thunk f) {