[FS#1003] Flex does not build with GCC 7.2

[LEDE Bugs]

The following task has a new comment added:

FS#1003 - Flex does not build with GCC 7.2
User who did this - Syrone Wong (wongsyrone)

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Please check these two commits:

https://github.com/westes/flex/commit/2b290d8ebdfa73b8f4665847fb689884eceee269
https://github.com/westes/flex/commit/f2943389fd3ca776d25735c06ef94512a2bb5c20

The fixes will be in 2.6.5
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1003#comment3480