package/qemu: fix static build

Fix the following static build failure raised since bump to version 6.1
in commit 33c69c02fb4c1176584d1e2dd336b74ed39f5d65 and
https://gitlab.com/qemu-project/qemu/-/commit/ba4dd2aabc35bc5385739e13f14e3a10a223ede0
(which enabled plugins by default):

Library dl found: YES
Checking for function "dlopen" with dependency -ldl: NO

../meson.build:460:4: ERROR: Problem encountered: dlopen not found

Fixes:
 - http://autobuild.buildroot.org/results/df447bd963e62e06b28d7230da744616ae55b194

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qemu/qemu.mk

@@ -167,6 +167,10 @@ else
 QEMU_OPTS += --disable-usb-redir
 endif
 
+ifeq ($(BR2_STATIC_LIBS),y)
+QEMU_OPTS += --static
+endif
+
 # Override CPP, as it expects to be able to call it like it'd
 # call the compiler.
 define QEMU_CONFIGURE_CMDS