add flex package

flex/Makefile

@@ -0,0 +1,15 @@
+prepare:
+	wget -O flex.tar.gz https://github.com/westes/flex/releases/download/v2.6.4/flex-2.6.4.tar.gz
+	tar -xf flex.tar.gz
+	cd flex
+make:
+	@./configure \
+		--prefix=/usr \
+		ac_cv_func_malloc_0_nonnull=yes \
+		ac_cv_func_realloc_0_nonnull=yes
+	make
+install:
+	make install DESTDIR="${PREFIX}"
+	ln -s flex "$1/usr/bin/lex"
+uninstall:
+	make uninstall