package/upmpdcli: append to _CONF_OPTS

check-package now gives a warning about this. It's not a problem at the
moment, but it's a risk if an unconditional setting of _CONF_OPTS is
done earlier in the file.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/upmpdcli/upmpdcli.mk

@@ -12,7 +12,7 @@ UPMPDCLI_DEPENDENCIES = host-pkgconf libmpdclient libupnpp libmicrohttpd jsoncpp
 
 # Disable spotify plugin which requires dlfcn.h
 ifeq ($(BR2_STATIC_LIBS),y)
-UPMPDCLI_CONF_OPTS = --disable-spotify
+UPMPDCLI_CONF_OPTS += --disable-spotify
 endif
 
 # Upmpdcli only runs if user upmpdcli exists