This avoids the following error when building under ubuntu 18.04
which has a never version of automake:
configure.ac:31: error: version mismatch. This is Automake 1.15.1,
configure.ac:31: but the definition used by this AM_INIT_AUTOMAKE
configure.ac:31: comes from Automake 1.15. You should recreate
configure.ac:31: aclocal.m4 with aclocal and run automake again.
+++ /dev/null
-diff -u -r ../flex-2.6.0/Makefile.am ./Makefile.am
---- ../flex-2.6.0/Makefile.am 2015-11-10 17:55:38.000000000 -0500
-+++ ./Makefile.am 2015-12-27 06:36:29.059725071 -0500
-@@ -53,7 +53,6 @@
- doc \
- examples \
- po \
-- tests \
- tools
-
- # Create the ChangeLog, but only if we're inside a git working directory
--- /dev/null
+diff -u -r ../flex-2.6.4/Makefile.in ./Makefile.in
+--- ../flex-2.6.4/Makefile.in 2017-05-06 16:49:09.000000000 +0200
++++ ./Makefile.in 2018-04-29 23:46:48.128733975 +0200
+@@ -453,7 +453,6 @@
+ doc \
+ examples \
+ po \
+- tests \
+ tools
+
+ all: all-recursive