package/asterisk: Fix build

Looks like there is a bug in AST_INLINE_API macro voodoo. Fix taken from
here: https://issues.asterisk.org/jira/browse/ASTERISK-25503

Signed-off-by: Phil Sutter <phil@nwl.cc>

package/asterisk/Makefile

@@ -111,7 +111,7 @@ INSTALL_STYLE:=		manual
 TARGET_CFLAGS+=		-fgnu89-inline
 TARGET_LDFLAGS+=	-lm -ltinfo -ldl -lpthread
 MAKE_ENV=		ASTCFLAGS="${TARGET_CPPFLAGS} -DHAVE_STRTOQ" \
-			ASTLDFLAGS="${TARGET_LDFLAGS}"
+			ASTLDFLAGS="${TARGET_LDFLAGS} -z muldefs"
 MAKE_FLAGS+=		DESTDIR="$(WRKINST)" \
 			OPTIMIZE="${TARGET_CFLAGS}" \
 			NOISY_BUILD=1