Add ability to disable precompiled headers with CMake (#2727)

src/providers/irc/Irc2.cpp

@@ -11,6 +11,8 @@
 #include <QSaveFile>
 #include <QtConcurrent>
 
+#include <unordered_set>
+
 namespace chatterino {
 
 namespace {

src/providers/irc/IrcCommands.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <QString>
 #include "common/Outcome.hpp"
 
 namespace chatterino {

src/providers/irc/IrcServer.cpp

@@ -11,6 +11,8 @@
 #include "singletons/Settings.hpp"
 #include "util/QObjectRef.hpp"
 
+#include <QMetaEnum>
+
 namespace chatterino {
 
 IrcServer::IrcServer(const IrcServerData &data)