coroutine: add a macro for the coroutine stack size

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/util/coroutine-win32.c b/util/coroutine-win32.c
index 02e28e8..de6bd4f 100644
--- a/util/coroutine-win32.c
+++ b/util/coroutine-win32.c
@@ -71,7 +71,7 @@
 
 Coroutine *qemu_coroutine_new(void)
 {
-    const size_t stack_size = 1 << 20;
+    const size_t stack_size = COROUTINE_STACK_SIZE;
     CoroutineWin32 *co;
 
     co = g_malloc0(sizeof(*co));