package/asterisk: fix compile issue

Fix a compile issue when libyuv and libjpeg is enabled.
Detection of following function fails:
checking for pjsip_dlg_create_uas_and_inc_lock in -lpjsip... no

In config.log you see that libjpeg is missing.

Fixes:
 http://autobuild.buildroot.net/results/7bed9fc68fc9331ad12942c3eab9742ee8a7a4c4

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/asterisk/asterisk.mk

@@ -113,9 +113,15 @@ ASTERISK_CONF_ENV = \
 
 # Uses __atomic_fetch_add_4
 ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
-ASTERISK_CONF_ENV += LIBS="-latomic"
+ASTERISK_LIBS += -latomic
 endif
 
+ifeq ($(BR2_PACKAGE_LIBYUV)$(BR2_PACKAGE_JPEG),yy)
+ASTERISK_LIBS += -ljpeg
+endif
+
+ASTERISK_CONF_ENV += LIBS="$(ASTERISK_LIBS)"
+
 ifeq ($(BR2_TOOLCHAIN_USES_GLIBC),y)
 ASTERISK_CONF_OPTS += --with-execinfo
 else