[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 - Simon Tretter (simontretter)

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Same issue here. Can't build the toolchain on Arch with gcc 7.2.0 due to this flex bug.
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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#comment3473