Remove guards around unistd.h

We take unistd.h for granted in many places, so remove guards around the
corresponding includes to make code consistent.

src/main.cpp

@@ -46,14 +46,10 @@
 #include <QTranslator>
 #include <QLibraryInfo>
 
-// system
-#if __has_include(<unistd.h>)
-#include <unistd.h>
-#endif
-
 #ifdef __has_include(<malloc.h>)
 #include <malloc.h>
 #endif
+#include <unistd.h>
 
 // xcb
 #include <xcb/damage.h>

src/main_x11.cpp

@@ -42,10 +42,8 @@
 #include <QtDBus>
 
 // system
-#if __has_include(<unistd.h>)
-#include <unistd.h>
-#endif
 #include <iostream>
+#include <unistd.h>
 
 Q_LOGGING_CATEGORY(KWIN_CORE, "kwin_core", QtWarningMsg)
 

src/xwl/xwayland.cpp

@@ -42,14 +42,10 @@
 #include <QTimer>
 #include <QtConcurrentRun>
 
-// system
-#if __has_include(<unistd.h>)
-#include <unistd.h>
-#endif
-
-#include <sys/socket.h>
 #include <cerrno>
 #include <cstring>
+#include <sys/socket.h>
+#include <unistd.h>
 
 namespace KWin
 {