hw/i386/xen: Compile 'xen-hvm.c' with Xen CPPFLAGS

xen-hvm.c calls xc_set_hvm_param() from <xenctrl.h>,
so better compile it with Xen CPPFLAGS.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20231114143816.71079-19-philmd@linaro.org>
1 file changed