必須ライブラリ

• m4
• autoconf
• Gettext
• automake
• bison
• help2man
• texinfo
• indent
• libtool?

$ wget https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz
$ tar xvf flex-2.6.4.tar.gz
$ cd flex-2.6.4/
$ export LIBTOOLIZE=/opt/libtool/2.4.6/bin/libtoolize 
$ ./autogen.sh 
$ ./configure --prefix=/opt/flex/2.6.4 CFLAGS='-g -O2 -D_GNU_SOURCE'
$ make
$ make install

# apt install flex