flex: disable building po, tools

Amend the patch that disabled tests and docs to remove everything but
the src dir that builds the main flex program--the only file packaged.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

devel/flex/patches/100-disable-all-dirs-except-src.patch

@@ -1,13 +1,16 @@
 --- a/Makefile.am
 +++ b/Makefile.am
-@@ -43,10 +43,7 @@ EXTRA_DIST = \
+@@ -42,12 +42,7 @@ EXTRA_DIST = \
+ 	autogen.sh
  
  SUBDIRS = \
- 	src \
+-	src \
 -	doc \
 -	examples \
- 	po \
+-	po \
 -	tests \
- 	tools
+-	tools
++	src
  
  # Create the ChangeLog, but only if we're inside a git working directory
+