wget https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz
tar -xf flex-2.6.4.tar.gz
cd flex-2.6.4

sed -i "/math.h/a #include <malloc.h>" src/flexdef.h
HELP2MAN=/tools/bin/true ./configure --prefix=/usr --docdir=/usr/share/doc/flex-2.6.4

make
make check
make install DESTDIR="$1"
ln -sv flex $1/usr/bin/lex