编译ffmpeg，出现如下错误：
libavfilter/avf_showcqt.c:35:10: fatal error: ft2build.h: 没有那个文件或目录
#include
^~~~~~~~~~~~
compilation terminated.
make: *** [ffbuild/common.mak:59：libavfilter/avf_showcqt.o] 错误 1
解决办法，修改ffbuild/common.mak：
# NASM requires -I path terminated with /
IFLAGS := -I/home/quantum6/lib-build/include/SDL2 \
-I/home/quantum6/lib-build/include \
-I/home/quantum6/lib-build/include/freetype2 \
-I. -I$(SRC_LINK)/
