[FS#194] lantiq: iproute2 fails to build on undefined constant PATH_MAX

[LEDE Bugs]

The following task has a new comment added:

FS#194 - lantiq: iproute2 fails to build on undefined constant PATH_MAX
User who did this - Knut Masanetz (Joe_Bar)

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Breaks the same way on x86_64 and ar71xx...
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=194#comment512