package/tcpreplay: fix build with musl-fts

Fix the following build failure with musl-fts raised since bump to
version 4.4.1 in commit cc66cf922b0481b66011b171db7985a27c79c381 and
https://github.com/appneta/tcpreplay/commit/e1f4c2ac9133584da4be0da855c04c314a2e68c2:

/home/giuliobenetti/autobuild/run/instance-1/output-1/host/opt/ext-toolchain/bin/../lib/gcc/powerpc-buildroot-linux-uclibc/10.3.0/../../../../powerpc-buildroot-linux-uclibc/bin/ld: tcpreplay-tcpreplay.o: in function `main':
tcpreplay.c:(.text.startup+0x21c): undefined reference to `fts_open'

Fixes:
 - http://autobuild.buildroot.org/results/e47940b5b158395329c0132bb1bbea429c4dc249

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

package/tcpreplay/tcpreplay.mk

@@ -11,14 +11,20 @@ TCPREPLAY_LICENSE = GPL-3.0
 TCPREPLAY_LICENSE_FILES = docs/LICENSE
 TCPREPLAY_CPE_ID_VENDOR = broadcom
 TCPREPLAY_CONF_ENV = \
-	ac_cv_path_ac_pt_PCAP_CONFIG="$(STAGING_DIR)/usr/bin/pcap-config"
+	ac_cv_path_ac_pt_PCAP_CONFIG="$(STAGING_DIR)/usr/bin/pcap-config" \
+	LIBS="$(TCPREPLAY_LIBS)"
 TCPREPLAY_CONF_OPTS = --with-libpcap=$(STAGING_DIR)/usr \
 	--enable-pcapconfig
 TCPREPLAY_DEPENDENCIES = libpcap
 
+ifeq ($(BR2_TOOLCHAIN_USES_GLIBC),)
+TCPREPLAY_DEPENDENCIES += musl-fts
+TCPREPLAY_LIBS += -lfts
+endif
+
 ifeq ($(BR2_STATIC_LIBS),y)
 TCPREPLAY_CONF_OPTS += --enable-dynamic-link=no
-TCPREPLAY_CONF_ENV += LIBS="`$(STAGING_DIR)/usr/bin/pcap-config --static --libs`"
+TCPREPLAY_LIBS += `$(STAGING_DIR)/usr/bin/pcap-config --static --libs`
 endif
 
 ifeq ($(BR2_PACKAGE_LIBDNET),y)