[FS#1391] lantiq: lib_ifxos fails to build with PIE with musl

[LEDE Bugs]

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FS#1391 - lantiq: lib_ifxos fails to build with PIE with musl
User who did this: Mathias Kresin (mkresin)
Summary: ld: unrecognized option '-specs=[...]/include/hardened-ld-pie.specs' when build with PIE with musl -> lantiq: lib_ifxos fails to build with PIE with musl

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1391