tests/qtest/fuzz: Fix build failure

On Fedora 32, using clang (version 10.0.1-3.fc32) we get:

  tests/qtest/fuzz/fuzz.c:237:5: error: implicit declaration of function 'qemu_init' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
      qemu_init(result.we_wordc, result.we_wordv, NULL);
      ^

qemu_init() is declared in "sysemu/sysemu.h", include this
header to fix.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210513162008.3922223-1-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tests/qtest/fuzz/fuzz.c

@@ -16,6 +16,7 @@
 #include <wordexp.h>
 
 #include "qemu/datadir.h"
+#include "sysemu/sysemu.h"
 #include "sysemu/qtest.h"
 #include "sysemu/runstate.h"
 #include "qemu/main-loop.h"