mpd: Try using older boost for older gcc <= 4.9.4

cross/mpd/Makefile

@@ -31,15 +31,22 @@ DEPENDS += cross/libshout
 DEPENDS += cross/opus
 DEPENDS += cross/soxr
 DEPENDS += cross/curl
-DEPENDS += cross/boost_1.82
+
+OPTIONAL_DEPENDS = cross/boost_1.68 cross/boost_1.82
 
 HOMEPAGE = https://www.musicpd.org/
 COMMENT  = Music Player Daemon (MPD) is a flexible, powerful, server-side application for playing music.
 LICENSE  = GPLv2
 
+include ../../mk/spksrc.cross-meson.mk
+
+ifeq ($(call version_lt, $(TC_GCC), 5),1)
+DEPENDS += cross/boost_1.68
+BOOST_BUILD_PATH=$(WORK_DIR)/boost_1_68_0
+else
+DEPENDS += cross/boost_1.82
 BOOST_BUILD_PATH=$(WORK_DIR)/boost_1_82_0
+endif
 BOOST_LIBRARIES += system
 ENV += BOOST_INCLUDEDIR="$(BOOST_BUILD_PATH)/boost"
 ENV += BOOST_LIBRARYDIR="$(BOOST_BUILD_PATH)/libs"
-
-include ../../mk/spksrc.cross-meson.mk