(#5) try to fix dynamic linking error cased by giflib

Makefile

@@ -9,7 +9,7 @@ endif
 # TODO(#87): we need an option to build with system libraries
 VODUS_PKGS=freetype2
 VODUS_CXXFLAGS=-Wall -fno-exceptions -std=c++17 $(VODUS_EXTRA_CXXFLAGS) -ggdb `pkg-config --cflags $(VODUS_PKGS)` -I./third_party/ffmpeg-4.3-dist/usr/local/include/ -I./third_party/giflib-5.2.1-dist/usr/local/include/
-VODUS_LIBS=`pkg-config --libs $(VODUS_PKGS)` -L./third_party/giflib-5.2.1-dist/usr/local/lib/ -lgif -L./third_party/ffmpeg-4.3-dist/usr/local/lib/ -lavcodec -lavutil -lswresample -pthread -lm -llzma -lz
+VODUS_LIBS=`pkg-config --libs $(VODUS_PKGS)` -L./third_party/giflib-5.2.1-dist/usr/local/lib/ ./third_party/giflib-5.2.1-dist/usr/local/lib/libgif.a -L./third_party/ffmpeg-4.3-dist/usr/local/lib/ -lavcodec -lavutil -lswresample -pthread -lm -llzma -lz
 
 ifeq ($(UNAME), Darwin)
 VODUS_LIBS += -framework AVFoundation -framework VideoToolbox -framework CoreVideo -framework AudioToolbox -framework CoreMedia -framework CoreFoundation -liconv