flex: update to 2.6.4 (FS#809)

flex 2.6.3 has a bug which fails code generation and compile of some packages

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

tools/flex/Makefile

@@ -7,11 +7,11 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=flex
-PKG_VERSION:=2.6.3
+PKG_VERSION:=2.6.4
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/westes/flex/releases/download/v$(PKG_VERSION)/
-PKG_HASH:=68b2742233e747c462f781462a2a1e299dc6207401dac8f0bbb316f48565c2aa
+PKG_HASH:=e87aae032bf07c26f85ac0ed3250998c37621d95f8bd748b31f15b33c45ee995
 
 HOST_BUILD_PARALLEL:=1