IPC: Add missing includes of errno.h

These files use errno constants such as EACCES, while relying on
this header to be included implicitly.

If building with the latest libc++ versions, configured with
_LIBCPP_REMOVE_TRANSITIVE_INCLUDES=1 (which removes unnecessary
transitive includes from the public headers), one runs into this
error, where errno.h no longer is implicitly included through
other headers.

Prior to 762017f, these functions
were in separate files that explicitly did include errno.h.

Change-Id: I7b02f2ffa35b86606f6c173bf6a6d2917dbdc151
Reviewed-by: Thiago Macieira <[email protected]>
Reviewed-by: Giuseppe D'Angelo <[email protected]>
(cherry picked from commit 9f42946)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

src/corelib/ipc/qsharedmemory.cpp

@@ -12,6 +12,7 @@
 #ifdef Q_OS_WIN
 #  include <qt_windows.h>
 #endif
+#include <errno.h>
 
 #ifndef MAX_PATH
 #  define MAX_PATH PATH_MAX

src/corelib/ipc/qsystemsemaphore.cpp

@@ -6,6 +6,7 @@
 
 #if QT_CONFIG(systemsemaphore)
 #include <QtCore/q20memory.h>
+#include <errno.h>
 
 QT_BEGIN_NAMESPACE