cutils: Add missing dyld(3) include on macOS

Commit 06680b15 moved qemu_*_exec_dir() to cutils but forgot
to move the macOS dyld(3) include, resulting in the following
error (when building with Homebrew GCC on macOS Monterey 12.4):

  [313/1197] Compiling C object libqemuutil.a.p/util_cutils.c.o
  FAILED: libqemuutil.a.p/util_cutils.c.o
  ../../util/cutils.c:1039:13: error: implicit declaration of function '_NSGetExecutablePath' [-Werror=implicit-function-declaration]
   1039 |         if (_NSGetExecutablePath(fpath, &len) == 0) {
        |             ^~~~~~~~~~~~~~~~~~~~
  ../../util/cutils.c:1039:13: error: nested extern declaration of '_NSGetExecutablePath' [-Werror=nested-externs]

Fix by moving the include line to cutils.

Fixes: 06680b15 ("include: move qemu_*_exec_dir() to cutils")
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220809222046.30812-1-f4bug@amsat.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>