crosstool-ng: Fix custom linux kernel headers support
crosstool-ng: Fix custom linux kernel headers support

With OE-lite v3, we need to use "target:" prefix, as default for cross
recipes is "cross:".

hundeboll/core,sknsean/core,sknsean/core,sknsean/core,hundeboll/core,diorcety/oe-lite-core,hundeboll/core,diorcety/oe-lite-core,sknsean/core,sknsean/core,hundeboll/core