graphicsmagick: optimize compilation

Use 'flto' compiler option to slightly reduce the installation
footprint.

Signed-off-by: Val Kulkov <val.kulkov@gmail.com>

multimedia/graphicsmagick/Makefile

@@ -6,7 +6,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=graphicsmagick
 PKG_VERSION:=1.3.31
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/GraphicsMagick-$(PKG_VERSION)
 PKG_SOURCE:=GraphicsMagick-$(PKG_VERSION).tar.bz2
@@ -72,6 +72,8 @@ CONFIGURE_ARGS += \
 	--without-zstd \
 	--without-x
 
+TARGET_CFLAGS += -flto
+
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include
 	$(CP) \