jsoncpp: add size optimizations

Reduces size slightly.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/jsoncpp/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=jsoncpp
 PKG_VERSION:=1.9.2
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://codeload.github.com/open-source-parsers/jsoncpp/tar.gz/$(PKG_VERSION)?
@@ -47,6 +47,11 @@ define Package/jsoncpp/description
   convenient format to store user input files.
 endef
 
+MESON_ARGS += \
+	-Db_lto=true
+
+TARGET_LDFLAGS += -Wl,--gc-sections
+
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include
 	$(CP) $(PKG_INSTALL_DIR)/usr/include/json $(1)/usr/include/