Fix detection of Yocto 1.7 sysroot
Fix detection of Yocto 1.7 sysroot

The 1.7 sysroot for wp85 is
 armv7a-vfp-neon-poky-linux-gnueabi
instead of
 armv7a-neon-poky-linux-gnueabi
on Yocto 2.2.

Since so far this is mostly hardcoded in the findtoolchain script,
the sysroot argument ends up being empty and it breaks.

Resolves: LE-10369
Change-Id: I117e7eac52362a85bf16c504c54251c9000c9c28

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af