package/clamav: fix clamsubmit linking

As suggested by Arnout in review of
https://patchwork.ozlabs.org/patch/1175732/, set OBJC to $(TARGET_CC)

Fixes:
 - http://autobuild.buildroot.org/results/49973b2283c65de5155deaf633cd6569a37af375

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/clamav/clamav.mk

@@ -22,7 +22,8 @@ CLAMAV_DEPENDENCIES = \
 # mmap cannot be detected when cross-compiling, needed for mempool support
 CLAMAV_CONF_ENV = \
 	ac_cv_c_mmap_private=yes \
-	have_cv_ipv6=yes
+	have_cv_ipv6=yes \
+	OBJC=$(TARGET_CC)
 
 ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
 CLAMAV_LIBS += -latomic