package/smcroute: don't override dependencies

Don't override SMCROUTE_DEPENDENCIES in a conditional

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 5c9764be06ff772dfa4bfbf860b936dbcd859640)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/smcroute/smcroute.mk

@@ -16,7 +16,7 @@ SMCROUTE_CONF_OPTS = ac_cv_func_setpgrp_void=yes
 SMCROUTE_MAKE_ENV = $(TARGET_CONFIGURE_OPTS)
 
 ifeq ($(BR2_PACKAGE_LIBCAP),y)
-SMCROUTE_DEPENDENCIES = libcap
+SMCROUTE_DEPENDENCIES += libcap
 SMCROUTE_CONF_OPTS += --with-libcap
 else
 SMCROUTE_CONF_OPTS += --without-libcap