Work around std::filesystem being unavailable on mac w/ warnings

The version of the macOS sdk we're using doesn't implement it,
 see more detailed in-code comment included in this commit

src/Etterna/Screen/Others/ScreenSelectMusic.cpp

@@ -37,7 +37,7 @@
 #include "Etterna/Actor/Gameplay/Player.h"
 #include "Etterna/Models/NoteData/NoteDataUtil.h"
 #include "Etterna/Singletons/ReplayManager.h"
-#include "Etterna/Screen/Others/ScreenPrompt.h"
+#include "Etterna/Screen/Others/ScreenPrompt.h"
 
 #include <filesystem>
 #include <algorithm>
@@ -484,12 +484,12 @@ ScreenSelectMusic::Input(const InputEventPlus& input)
 					if (CachePackForRanking(GAMESTATE->m_sLastSongGroup))
 						return true;
 				} else {
-					// most likely hovering a non pack section
+					// most likely hovering a non pack section
 				}
 			} else {
 				if (CachePackForRanking(GAMESTATE->m_pCurSong->m_sGroupName))
 					return true;
-			}
+			}
 		} else if (bHoldingCtrl &&
 				   input.DeviceI.button == KEY_BACK &&
 				   input.type == IET_FIRST_PRESS && m_MusicWheel.IsSettled()) {
@@ -950,11 +950,11 @@ ScreenSelectMusic::ChangeSteps(PlayerNumber pn, int dir)
 void
 ScreenSelectMusic::HandleMessage(const Message& msg)
 {
-	if (msg == Message_FavoritesUpdated) {
+	if (msg == Message_FavoritesUpdated) {
 		// this makes the favorite icon appear if the wheel isnt moving
 		if (m_MusicWheel.IsSettled()) {
 			m_MusicWheel.RebuildWheelItems(0);
-		}
+		}
 	}
 
 	ScreenWithMenuElements::HandleMessage(msg);
@@ -1143,6 +1143,12 @@ ScreenSelectMusic::HandleScreenMessage(const ScreenMessage& SM)
 void
 ScreenSelectMusic::OnConfirmSongDeletion()
 {
+	//Temporary hacky workaround -- std::filesystem is unavailable before the macOS 10.15 sdk, and we're currently using an old sdk for backwards compatibility.
+	//Do nothing until this is properly implemented
+#if defined(__APPLE__)
+	#warning "ScreenSelectMusic::OnConfirmSongDeletion is unimplemented for mac target!"
+	Locator::getLogger()->warn("Deleting songs unimplemented on macOS!  (ScreenSelectMusic::OnConfirmSongDeletion)");
+#else
 	auto* deletedSong = m_pSongAwaitingDeletionConfirmation;
 	if (!deletedSong) {
 		Locator::getLogger()->warn("Attempted to delete a null song (ScreenSelectMusic::OnConfirmSongDeletion)");
@@ -1155,14 +1161,14 @@ ScreenSelectMusic::OnConfirmSongDeletion()
 	const std::filesystem::path songDir = std::filesystem::u8path(p);
 
 	// flush the deleted song from any caches
-	SONGMAN->UnlistSong(deletedSong);
-
+	SONGMAN->UnlistSong(deletedSong);
+
 	// stop the music because this holds a file handle
 	SOUND->StopMusic();
-	SOUND->Flush();
+	SOUND->Flush();
 
 	// refresh the song list
-	m_MusicWheel.ReloadSongList(false, "");
+	m_MusicWheel.ReloadSongList(false, "");
 
 	// delete the song directory from disk
 	Locator::getLogger()->info("Deleting song directory: {}", songDir.generic_string());
@@ -1177,11 +1183,12 @@ ScreenSelectMusic::OnConfirmSongDeletion()
 		Locator::getLogger()->error("There was an error while trying to remove "
 									"the song directory {} - {}",
 									songDir.generic_string(),
-									e.what());
+									e.what());
 	}
-	m_pSongAwaitingDeletionConfirmation = nullptr;
+	m_pSongAwaitingDeletionConfirmation = nullptr;
 
 	MESSAGEMAN->Broadcast("DeletedCurrentSong");
+#endif
 }
 
 bool
@@ -1382,7 +1389,7 @@ ScreenSelectMusic::AfterMusicChange()
 		GAMESTATE->m_pCurSteps.Set(nullptr);
 		if (GAMESTATE->m_SortOrder == SORT_GROUP) {
 			// when hovering groups, set group to the hovered one
-			GAMESTATE->m_sLastSongGroup = m_MusicWheel.GetSelectedSection();
+			GAMESTATE->m_sLastSongGroup = m_MusicWheel.GetSelectedSection();
 		}
 		if (b_PreviewNoteFieldIsActive)
 		// if previewnotefield we are moving out of a pack
@@ -1602,15 +1609,15 @@ ScreenSelectMusic::PauseSampleMusic()
 		// us we didnt really pause anything (wow who would have thought)
 		GAMESTATE->SetPaused(success && pMusic->m_bPaused);
 	});
-}
-
+}
+
 bool
-ScreenSelectMusic::DeleteCurrentSong()
+ScreenSelectMusic::DeleteCurrentSong()
 {
 	Song* songToDelete = GAMESTATE->m_pCurSong;
 
 	if (songToDelete != nullptr && PREFSMAN->m_bAllowSongDeletion.Get()) {
-		m_pSongAwaitingDeletionConfirmation = songToDelete;
+		m_pSongAwaitingDeletionConfirmation = songToDelete;
 
 		ScreenPrompt::s_bMustResetInputRedirAtClose = true;
 		ScreenPrompt::Prompt(SM_ConfirmDeleteSong,
@@ -1749,8 +1756,8 @@ ScreenSelectMusic::AddCurrentChartToActivePlaylist()
 			   GAMESTATE->m_pCurSong->GetDisplayMainTitle().c_str(),
 			   SONGMAN->activeplaylist.c_str()));
 	return true;
-}
-
+}
+
 bool
 ScreenSelectMusic::CachePackForRanking(const std::string& pack)
 {
@@ -2044,7 +2051,7 @@ class LunaScreenSelectMusic : public Luna<ScreenSelectMusic>
 	{
 		p->PlayCurrentSongSampleMusic(true, BArg(1), BArg(2));
 		return 0;
-	}
+	}
 	static int DeleteCurrentSong(T* p, lua_State* L)
 	{
 		lua_pushboolean(L, p->DeleteCurrentSong());
@@ -2079,15 +2086,15 @@ class LunaScreenSelectMusic : public Luna<ScreenSelectMusic>
 	{
 		lua_pushboolean(L, p->AddCurrentChartToActivePlaylist());
 		return 1;
-	}
-	static int CachePackForRanking(T* p, lua_State* L)
+	}
+	static int CachePackForRanking(T* p, lua_State* L)
 	{
 		if (lua_isnoneornil(L, 1)) {
 			lua_pushboolean(
 			  L,
-			  p->CachePackForRanking(p->GetMusicWheel()->GetSelectedSection()));
+			  p->CachePackForRanking(p->GetMusicWheel()->GetSelectedSection()));
 		} else {
-			lua_pushboolean(L, p->CachePackForRanking(SArg(1)));
+			lua_pushboolean(L, p->CachePackForRanking(SArg(1)));
 		}
 
 		return 1;