libdouble-conversion: Size optimizations

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

libs/libdouble-conversion/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libdouble-conversion
 PKG_VERSION:=3.1.5
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE:=double-conversion-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://codeload.github.com/google/double-conversion/tar.gz/v$(PKG_VERSION)?
@@ -48,6 +48,9 @@ CMAKE_OPTIONS += \
 	-DBUILD_SHARED_LIBS=ON \
 	-DBUILD_TESTING=OFF
 
+TARGET_CXXFLAGS += -ffunction-sections -fdata-sections -fno-rtti -flto
+TARGET_LDFLAGS += -Wl,--gc-sections
+
 define Package/libdouble-conversion/install
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/lib*.so* $(1)/usr/lib/